Category Archives: Safety

Ensuring Thermal Process Safety in Chemical Manufacturing

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In my industrial career as a PhD organic/organometallic chemist I was kept busy for about 10 years with in-house Reaction Calorimetry (RC), Accelerating Rate Calorimetry (ARC), Differential Scanning Calorimetry (DSC) as well as Thermogravimetric Analysis (TGA) for validating thermal process safety. To institutionalize this I was asked to start a process safety department and began standardizing experimental protocols and a database for the results. I was able to scour the internet for thermochemical papers, looking for mentions of energetic properties. As always, much can be learned by just looking around.

Thermal process safety refers to safe operation of chemical manufacturing in regard to the generation of heat in a reaction mass and the hazards arising therein. The hazards from uncontrolled self-heating include acceleration of reaction kinetics producing accelerating heat and pressure evolution. If the reaction enthalpy and subsequent temperature rise theoretically exceeds the boiling point of the solvent despite the cooling jacket and the chilled condenser, then self-heating can lead to a boil up and uncontrolled ejection of the reaction mass. With insufficient cooling, the temperature will rise to the solvent bp and boil off the solvent first, carrying much heat away as heat of evaporation. Once most of the solvent has boiled away and if the reaction mass continues to self-heat, the temperature will continue to rise and peak at some undesired level as the reactants are consumed. Further heating of the now hot, highly concentrated reaction mass, potentially leading to successive reactions that may or may not be exothermic.

When a liquid phase reaction mass self-heats faster than heat can be removed, the reactor pressure will begin to rise. As pressure builds, the boiling point of the reaction mass begins to rise, slowing down the boil-off. A sudden drop in pressure, as with the burst of a rupture disk, will cause a superheated solution to promptly boil throughout the reaction mass. This means that flash vaporization can lead to bubble formation throughout the volume of the reaction mass producing a foam. The severity will depend on the pressure drop and the bp of the solvent. If the headspace is sufficiently small, the foam can expand rapidly and begin to exit through the vent pipe. A properly engineered vent pipe has been sized to vent gas/vapor at specified conditions. Since a foam is part liquid and part gas/vapor, it lacks the overall compressibility of a gas/vapor so the resulting foam flow may be lower than calculated for a gas/vapor, slowing the rate of depressurization.

The distinction between gas and a vapor is that a vapor may be condensable as with most solvent vapors, but evolved gases like hydrogen, methane or carbon dioxide will combine with a non-condensable blanket gas like nitrogen and resist condensation in the by the chiller. The point is that if one is relying on a chilled condenser to knock down non-condensable gases as a pressure management control, then a rude shock is headed your way, especially if the rupture disk bursting pressure is higher than need be.

Flow into vent pipes that exit outdoors may discharge hot reaction mass onto the roof or wherever the vent terminates. If the vent terminates into a knockdown drum or other catch vessel, the hot reaction mass contacts whatever may be in those vessels.

Image: Mettler Toledo. The Mettler-Toledo RC1 rigged for dual feed and distillation or reflux. The two brown bottles (lower right) sit on balances and feed from two reagent bottles into the reactor (lower left). The feed of liquid reactants is pre-programmed and is controlled quite accurately. Reagents are fed into an agitating reaction mass (yellow) while the temperature and enthalpy (H or h) are monitored on the fly. The instrument monitors the jacket and reactor temperatures and with the help of heat capacities, Cp, can display the enthalpy of the reaction as it proceeds.

Fortunately, the thermal profile leading up to the above scenario can be modeled in properly conducted RC1 experiments. But exactly what can be done beforehand?

First, let’s realize that the total self-heating temperature rise can be measured. We add that ΔT (temperature rise) to the proposed reaction temperature Tr and get a maximum temperature of the synthetic reaction, MTSR. Once we have this, if the MTSR is greater than the bp of the solvent(s), then we know that an uncontained runaway is possible. What to do then?

  • R&D needs to justify the problematic low boiling solvent with the reaction temperature to be applied.
  • R&D needs to provide input on lowering the design reaction temperature.
  • Is a lower Tr for a longer reaction time feasible?
  • How sensitive is the reaction to a higher bp solvent substitution?
  • If the chosen solvent conveniently forces side or waste products to precipitate and be removed by filtration, then we have the conundrum of safety vs efficient processability.
  • The magnitude of the hazard in the minds of everyone involved may be quite different and will require a documented decision process. Engineering input here is invaluable.
Thermal runaway profile. Source. The linked article is well written.
  • Tp Process Temperature
  • ΔTad Adiabatic Temperature rise
  • MTSR Maximum Temperature of the Synthetic Reaction
  • TMRad Adiabatic Time to Maximum Rate
  • Tx Time of Cooling Loss

What if the design solvent is truly required for a feasible and economic process? This needs to be discussed first with chemists and engineers in the room and a decision rendered. If chemist input says no solvent change is desirable or economic, the engineers need to speak up as to whether there is an engineering work around. If a ready engineering work around is not feasible and the product is still important, then the chemists need to be challenged to find procedure that denies the equipment a runaway condition.

If we’re lucky, a partial batch reaction method can be used wherein the reactor is charged with solvent and most of the reactant compounds are in the vessel at the beginning of the run. The final reactant is slowly fed into the reactor and the reaction temperature is controlled by the feed rate. Reaction calorimetry can be used to arrive at a plausible maximum feed rate that is fast but not too fast. A reaction calorimeter is basically a chemical reaction detector and can be used to look for an approximate reaction onset temperature. Remember that onset temperature is not a physical or chemical property. It depends on the detection equipment and the rate of heating.

Like everything else, success can depend on first asking the right questions. On the graphic computer display of the RC1, you can determine the response to an aliquot of reagent addition. Does the heat production, q, rise promptly with addition or does it lag? If there is a lag or a latency, it means that over-charging by operators at scale can happen if they are looking for a prompt “heat kick” on addition of the feed.

The RC1 can also show the length of time to react away the feed or what the total reaction time may be If the reaction has a natural response lag, then a defined charge mass is called for. A response lag may also be due to the presence of water which must first be quenched under the reaction conditions. The most insidious situation is when the feed reactant accumulates in the reactor over the course of the reaction. This is very difficult to judge by the operators. The feed may accumulate until the reaction suddenly begins and accelerates out of control. This is not uncommon.

Finally, a proper “batch reaction” is one in which all of the reactants are loaded into the reactor all at once, the temperature is adjusted and the reaction begins. It is critical that before a new batch reaction is allowed, the chemists must show that this will not result in a runaway condition. This is where reaction calorimetry shines. The safety of a batch reaction is reproduced in the RC1and the progress is monitored. The RC1 can also be used to explore various reaction conditions to see if runaway potential can be easily blundered into. How narrow are the safe operating parameters? Many plant incidents happen at shift changes where the continuity of watchfulness may diverge for a time, even with automation.

TMRad Adiabatic Time to Maximum Rate

A very informative piece of data to have is the TMR- Time to Maximum Rate. This can be obtained by an Accelerated Rate Calorimeter or ARC. The instrument consists of a furnace into which is placed a sample “can” which can be made of metal or glass. The furnace raises the sample temperature gradually using a heat-wait-search (HWS) method searching for an onset temperature.

Once an onset temperature is found, the HWS is automatically halted and the furnace keeps adjusting its temperature to match the rising internal sample temperature. If the internal sample temperature and the exterior furnace temperature are the same, then the sample is under adiabatic conditions and no heat flows in or out of the sample can. The sample temperature is driven by self heating only.

Knowing the sample mass and the best guess at Cp, constant pressure heat capacity, the reaction enthalpy can be determined. From the data, the Time to Maximum Rate (TMR) can be calculated to give an equation. It is the time that a substance that is self-reacting takes to reach the maximum rate of heat output as a function of sample temperature. The instrument also records sample pressure. If the sample pressure does not return to ambient pressure at room temperature, this would mean that a non-condensable gas was evolved.

Image of the Phi-Tec II ARC system. from H.E.L. company. My ARC experience is with this model.

A typical ARC experiment took me from 6 to 24 hours to complete the HWS routine.

What TMR data allows one to do is to find a reaction temperature the reaches maximum rate in 24 hours or more. You plug in a temperature and you get a TMR. The temperature needed to produce a TMR of 24 hours is considered by many in industry to be the uppermost safe processing temperature. It helps to answer what the maximum safe temperature in which a solid can be dried before decomposition begins.

To outsource safety testing or not

First and foremost, a commercial safety test lab understands and uses procedures that are agreed upon and standardized. Also, if down the road there comes a related event, your response to criticism will be to refer to the test lab experts, not some ham fisted employee monkeying around in the lab doing improvised experiments. Certain safety matters should be referred to the commercial lab experts for valid results and for CYA. This applies especially to energetic materials like nitroaromatics or nitrate esters.

Chemical manufacturing is conducted at many scales from laboratory gram scale products for R&D, multi-kilogram kilo-lab batch processing to the colossal commodity scale continuous manufacturing of petrochemicals, agrichemicals, polymers, flavors & fragrances, and pharmaceuticals. Nearly all of these commodity chemicals and polymers are well known and have safety issues related only to flammability, exposure and dose.

Outsourcing tests that can be done inhouse is a missed opportunity to accumulate more skills which is company treasure. I’m speaking of calorimetry. Calorimeters can be brought on-site and meshed in with research and development. Just learning how to interpret thermograms alone brings workers new insights into their chemistry.

What is best for your company? In-house safety testing or outsourced safety testing? Like nearly everything else in life, the answer depends on the situation. If you need to survey for explosive hazards for the first time, there are several competent commercial labs available that will use standard protocols. My experience is that they employ just engineers or a mix of chemists and engineers. They conduct standard testing protocols wherein a series of samples are exposed step-wise to a series of ever increasing stimuli intensity to find the boundary conditions of sensitivity to various stimuli, like heat, friction, impact, dust explosion parameters, burn tests, static charge lifetimes and minimum ignition energy (MIE) with electrostatic discharge.

Explosibility testing

Sensitivity to explosive behavior is tested in numerous ways to flesh out the sensitivity profile. Testing is performed in stages where the least intense stimuli are tried first to screen for highly sensitive substances. The results of any single test run are graded as ‘Go/No Go’ or ‘positive/negative’. The terms ‘Go’ or ‘Negative’ mean that an explosive property was observed.

Part of explosives testing is finding out what kinds of stimuli lead to initiation of an explosion. The Bureau of Mines (BOM) drop weight test looks for the maximum safe impact energy. There is a friction test, an electrostatic discharge test, and many others. If the sample does not give a Go result at the maximum machine impact or friction, then it is regarded as safe under those precise conditions. In the BOM test, the higher the number (in drop distance of a 5 or 10 kg weight), the more stable it is to impact.

You get the testing data. Now what?

Now how do you take numerical test data and convert it to safer operations? This is where engineers can be most useful. Imagine a substance that has a 34 inch BOM drop weight result with a 10 kg anvil. Will any process equipment mash down on the substance inadvertently? Put this ball in the court of engineers and let them chew on it. This data moves workers closer to confidence in safety.

Outsourcing safety testing and explosive screening can lead to a conundrum. Outsourcing anything means that certain expertise may not be internalized for your company’s use, the user or manufacturer. Commercial labs will absolutely not comment on how the material can be safely used, whether or not it is too dangerous or nominally safe under your use conditions. Safe use is not an endorsement they will make, they will only stand behind their results from standard testing protocols. I’d do the same.

Before safety testing you were alone. Now, with safety data, you are still alone but with numbers. Engineers and plant operators are invaluable in locating equipment that delivers impacts or friction. They can also help to identify non-grounded equipment that may generate or accumulate electrostatic charge. Always get the plant people involved.

It didn’t take long to realize that if we sent samples out to commercial labs for calorimetry testing, the samples were subjected to unfamiliar standard test methodology. Early on it was fascinating to see what kind of experimental setups were used and what the results looked like. Being a synthesis chemist I was unfamiliar with calorimetry. My earlier exposure to calorimetry was limited to what appeared in molecular dynamics and mechanics modeling. Acquiring actual data on reaction enthalpies and onset conditions myself awakened a fascination that carried me far into reaction calorimetry and thermochemistry.

What was not clear at the outset of receiving external calorimetric, electrostatic and explosive test data was what to do with it. Using external hazard data to inform operational procedure was new to everyone. Yes, we could learn from an ARC experiment what temperature the onset to a runaway condition begins, but how to use the measurements in practice wasn’t always obvious.

Incidents have three phases- initiation, propagation and termination. You have to ask this: if an incident initiates, what is the preferred propagation direction to termination? Yes, this can be controlled somewhat but only in advance. For instance, if an explosion happens, what is the least terrible direction for the blast to go? These matters should be considered in the design phase of construction of a chemical facility. If they weren’t, then decisions must be made despite the lack of preplanning.

As an example, a commercial explosives company I’m aware of built their manufacturing facility out in the European countryside. Explosive materials were prepared, stored and handled in small buildings distributed over a large area with distance, berms and trees separating them. If an explosion happened, the blast wave would be isolated from other assets and attenuated by distance, berms and forest. Here, the propagation phase was suppressed by distance and topography.

Another explosion highlights the folly of not segregating manufacturing operations. A plant manufacturing a hydroxylamine called HOBT suffered a catastrophic incident where a reactor blew apart explosively during a process previously performed many times. The reactor was housed in a structure that had expanded over time by adding manufacturing space by piecemeal addition as needed. This resulted in a building that was a rabbits warren of rooms and hallways even including admin space. The explosion did not just happen without warning. The reactor began to overheat from accumulating heat of reaction and became unresponsive to cooling efforts by the operator. As the operator turned to go get help, the reactor exploded sending parts up and out of the building, with the agitator landing on the roof of an adjacent business and onto railroad tracks. Heat transfer oil ran out of the building and flowing into the nearby river. The operator was blown through a sheet rock wall but survived. The shock wave propagated into adjacent spaces and down hallways, blowing out windows, internal and external doors including overhead doors.

The sad thing is that another plant suffered a devastating explosion 20 years earlier making the same hydroxylamine product. Perhaps lessons were learned at this plant, but those lessons didn’t to the other plant.

The lesson is clear. In chemical manufacture the R&D folks must be sure that all chemical properties are well understood and such knowledge is a part of accessible in-house expertise. If there is no R&D, meaning that a large scale procedure is simply written up and performed without the scrutiny of cold expert eyes evaluating it, then you are stepping onto a high wire without a net. Both plants making the hydroxylamine had experienced chemists on site and performed the procedure without incident many, many times. Even then, incidents happened but how many incidents were averted by expert judgement? We’ll never know.

Experience

Let’s talk about experience. Career chemists are like everyone else- they may have accumulated years of experience. Some of the learning’s a person has accumulated are captured in writing and available to staff. Other learning’s reside in a person’s head only and are perhaps regarded as ‘obvious’. Or the serious hazards are actually disclosed on the Safety Data Sheet which was filed away without scrutiny. Knowledge of explosibility of a particular substance could be too narrow by virtue of time and obscurity to serve as walking around knowledge by many chemists. Some of us are accustomed to spotting explosive functional groups (explosophores) on a molecule but many are not.

For some individuals, their 18 years of experience is better described as 6 years repeated twice, or worse. Years of experience should always imply years of continuous improvement.

The main reason that process safety was a separate department was to prevent production and R&D from having vested interest in how test measurement results were interpreted and used or ignored. If calorimetric data suggests that a particular process reaction can run away or if a reaction should be initiated and run at a lower temperature, managers personally responsible for productivity may object owing to increased plant time or lower processing yields. This is especially problematic if prior experience has never shown a hint of a hazard, yet. Or, incidents in the past were not taken seriously or properly understood. The phrase “we’ve always done it this way” can be a very difficult barrier to overcome. And even if overcome, can revert back to the old practices over time.

This forces management to deal with safety margins and acceptable risk. They should automatically understand that zero risk is not possible. However, they may look back over the production history and not realize that they spent too much time near the edge of disaster.

Unknown risks

Imagine wearing a blindfold while standing 2 meters from the rim of the Grand Canyon. Someone turns you around a few times to scramble your senses. Now, even while not knowing the location of the rim, it is possible to walk around blindfolded and not go over the edge. You could do this for a short or a long time period and not fall in. Slowly you begin to doubt the hazard is real since you have not gone over the edge. Soon the risk is forgotten in the frenzy to reduce costs. Then one day you fall into the canyon and on the way down you muse about your own folly.

The Tylenol Debacle

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RFK, Jr., and his overlord, the Orange Jesus, have announced a possible link between acetaminophen and ADHD and autism. When they announced it, the trade name Tylenol was used. We can be certain that it went over like a lead balloon in the acetaminophen manufacturer’s world. But, first things first: Myth Busters were able to get a balloon made of lead sheets to actually float.

Lead balloon from Myth Busters episode. Source: Adam Sandler, YouTube.

It was announced that the FDA will be adding language to acetaminophen packaging warning. of the risk of ADHD and autism. To be sure, acetaminophen is capable of causing injury to the liver when an overdose is taken. Snakes in particular are very sensitive to acetaminophen poisoning. The island of Guam embarked on a program to rid the island of the invasive brown tree snake. A total of 2000 mice laced with acetaminophen were air-dropped over Guam in 2013 in an attempt to knock down the population on the island. The linked article did not mention the success rate. In addition to hepatotoxicity, apparently acetaminophen also converts hemoglobin to methemoglobin in just a few hours. Scientific details were behind a paywall which I generously leave to the reader to scale.

Our hospitals and medical staff prescribe acetaminophen because it does not interfere with blood clotting like the NSAIDS do. The makers of acetaminophen would like us to believe that their product is a superior pain reliever or anti-inflammatory to aspirin or ibuprofen. Decide for yourself.

How long will Kennedy continue to make faulty assertions, generally? As long as King Louie continues to keep him in the cabinet.

Disney’s King Louie. Source: Wikipedia.

Also, don’t forget. In Ohio they’re eating the cats … they’re eating the dogs.

Machismo and Violence

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The present situation is one whereby a large swath of the population, including K-12 students, are being exposed to an increased risk of bloody, violent death sustained by those who fetishize firearms. Whatever you may think of the 2nd Amendment to the US Constitution, the fact is that we are prioritizing an originalist interpretation over the lives of school children. We are allowing children to be sacrificed on the alter of the 2nd Amendment in order to satisfy people who idolize the idea of boundless access to metal tubes that discharge high energy bits of metal. We are not officially at war defending our borders in the US nor are we on the verge of a civil war. By far, most guns are not used to hunt. Most Americans lead peaceful lives in their neighborhoods without the need to shoot at people.

The very notion that the US government is going to wrench guns away from citizens in one of the most heavily armed democratic countries in the world is the fever dream of a fool. Any full-scale attempt to do this would lead to armed rebellion and the collapse of the USA as a democratic republic. Widespread gun confiscation is not politically feasible today or in the foreseeable future.

We must tone down and be less tolerant of the image of inflated machismo that guns confer to their users. Both in real life and in entertainment, gunplay is used to resolve conflict. By far, most gun owners do not commit violent acts with their guns. While they should not be penalized for the crimes committed by others, accepted mechanisms like driver’s and pilot’s licenses are a form of limitation and standardization that could be applied to access to firearms. But this reliably produces hysteria among the armed public. Like everything else in society, a few people have to ruin it for the rest of us.

The basic utility of a gun is to deliver crippling or fatal kinetic energy, or the threat of it, from a safe distance. The need for guns for peacekeeping use will last as long as there is dangerous criminality. What the US is presently suffering from is the use of rapid-fire, high-energy projectiles from guns designed to hit as many targets as possible in the shortest time. Man killers.

Sidebar

I took the hunter’s safety course sponsored by the NRA at the age of 9. The truth is that firing a gun is both fun and stimulating. I recall stealthily walking along a muddy creek in the Iowa countryside with a bolt action 0.22 caliber rifle desperately looking for some reason the fire the gun. I spotted fish, turtles and birds but something held me back from shooting at them except for once a few years later. With a BB gun I shot a sparrow perched on a small twig of an elm tree. The bird rotated backwards, still gripping the twig, and hung upside down for a minute or two. Then it released and dropped into an irrigation ditch with a small splash.

I was immediately gripped with regret and sorrow for what I had just done. I had just killed a random sparrow for utterly no reason than to see what happens. Even as a teenager I could see that this was a senseless action. I am sorry for killing the sparrow to this very day and, except for a few mice and bugs, I have never killed wildlife since.

Back to the essay

The point of the story above is that, for me, being in possession of a firearm could sometimes produce a strong urge to fire it. I’m confident that there are others who have felt the same way. The healthy release is to do target practice. Some people enjoy hunting. I do not indulge in this because I prefer the flavor of beef, pork and fish which, conveniently, are already butchered.

Male characteristics can have both good and bad attributes. A measure of focused male aggressiveness, ambition and territoriality can be beneficial for the wellbeing of loved ones and the community. Brute strength can be quite useful in providing for a family. Male rage, however, can be very destructive wherever it is directed, as we all know. A firearm or other weapon is a force multiplier for a raging male. Recent mass killings prove the point. Firearms provide the ability to kill or wound from a safe distance and the value of this is lost on no one.

It is hard to imagine that some restraint in the use of firearms without addressing the cultural and natural phenomenon of male aggression can be successful. We are saturated with violence in entertainment, on the streets and in the news. As long as we seek entertainment violence, show business will anxiously provide it.

I’m neither a Quaker nor a pacifist but I do admire their sincere dedication to non-violence. We need many early adopters of non-violence with considerable social standing and a non-violence vibe across the whole country. Destructive male behavior can be tamed to a great extent, but it has to start early and be immersed in non-violent surroundings. Where is the sign that Americans can summon the discipline to do it. I’m not seeing it.

EPA Suspends all US Registrations of Dacthal Herbicide

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The Environmental Protection Agency announced on August 6th, 2024 there would be an emergency suspension on all registrations of the preemergent herbicide chlorthal-dimethyl, or dimethyl tetrachloroterephthalate (DCPA or Dacthal). It has been 40 years since the US EPA has issued such an emergency suspension of registrations. This order has immediate effect.

US patent US2923634A was granted to Diamond Shamrock 1960-02-02 with a single claim-

1. THE METHOD OF CONTROLLING UNDESIRABLE PLANT GROWTH WHICH COMPRISES CONTACTING SAID PLANT GROWTH WITH AN ACTIVE AMOUNT OF DIMETHYL 2,3,5,6-TETRAHALOTEREPHTHALATE.

An early patent claiming the use of DCPA, but not the composition.

Graphic and physicochemical data. PubChem. DCPA structure tilted just a bit for clarity. Octanol/water partition coefficient: log KOW = 4.40 @ 25 °C, water solubility = 0.5 mg/l @ 25 °C, Vapor pressure: 2.5 x 10-6 mm Hg at 25 °C

The octanol/water partition coefficient, log KOW, sometimes called Log P, is a measure of how a substance will partition itself between 2 phases, a hydrophilic phase and lipophilic phase. This logarithm is used to give some insight into the type of living tissues a substance will tend to accumulate in on exposure or dosing. A log KOH of 4.40 represents a ratio (antilog) of 25,119 to 1 favoring the octanol. This indicates considerable lipophilicity.

The industrial manufacture of DCPA is neither complicated nor difficult. The terephthaloyl chloride (pronounced: terra THAL oh ill chloride, soft TH as in “thing”) raw material is used in the manufacture of Kevlar and is readily made in several ways. Whether or not the DCPA manufacturer makes their own or outsources it is not available information. In either case, the terephthaloyl chloride is chlorinated to exhaustion (fully chlorinated) and then the methyl ester is prepared by contacting the chloride with methanol to form the diester (pronounced: DYE ester).

Why does DCPA have 4 chlorine atoms on it? Hard to say exactly what the thinking was, but from the process chemistry perspective forcing 4 chlorine atoms on the ring rather than just 1, 2, or 3 solves the problem of ending up with a dog’s lunch of mono-, di-, tri- and tetrachlorinated compounds in the product mix. Individually, each may have differing potency, selectivity, biochemical mechanisms, and human or environmental toxicological properties. Subsequent environmental and tox studies would be complicated by the potential of 4 analogs each possibly requiring individual testing at some point. Another thing to consider is that single component solids are much more easily purified by crystallization than a solution of solid components. A solution of mixed components can be quickly precipitated by cooling or concentrating, but pulling out one pure solid among many solid close analogs can be difficult and low yielding. Single component products are almost always better for ease of processing.

Graphics by John Jacob Jungleheimer Schmidt. The “oyl” fragment of the name indicates the presence of the acid chloride group.

DCPA is a selective non-systemic, or contact, herbicide used for pre-emergence control of annual grasses and some annual broad-leaved weeds. Coverage rates of 6-14 kg/hectare are common.

From PubChem: “/IT IS/ PRESENTLY APPROVED FOR USE ON TURF, ORNAMENTALS, STRAWBERRIES, AND AGRONOMIC CROPS INCLUDING COTTON, SOYBEANS, AND FIELD BEANS. /IT IS/ EFFECTIVE AGAINST SMOOTH & HAIRY CRABGRASS, WITCHGRASS, GREEN & YELLOW FOXTAILS, FALL PANICUM & OTHER ANNUAL GRASSES. /IT IS/ ALSO USEFUL AGAINST CERTAIN BROAD-LEAVED WEEDS SUCH AS CARPET WEED…PURSLANE & COMMON CHICKWEED. /IT IS/ TOLERATED BY MANY CROP PLANTS.”

DCPA is a relatively simple small molecule that is made from cheap and abundant early feedstocks like para-Xylene, Chlorine and Methanol. It has good potency and desirable selectivity in its ability to kill crabgrass in the presence of turf grass. The chemical process steps are well understood, each with a long history of successful use. It can be sold in solid form or in liquid form and may be applied by a large variety of methods. It can be applied for pre-emergence or folial use.

According to EPA “DCPA is a chlorinated benzoic acid herbicide which inhibits cell division of root tips in target plants. It controls many annual grasses and broadleaf weeds in a variety of agricultural crops and ornamental varieties (e.g., broccoli, onions, tomatoes, cabbage, cauliflower, dogwood, azalea). Annual agricultural use from 1998 through 2008 averaged approximately 500,000 pounds over 100,000 acres with broccoli and onions accounting for 79 percent of that use (Ratnayake, 2011). Information also suggests that on average 50 percent of broccoli is treated and 15 percent of onions (SLUA).“

As useful of an herbicide as it may be, it has a dark side that spooked the US EPA into issuing an unusual emergency suspension on August 6, 2024. In particular is the potential toxicity to the unborn and the risk to “post-application workers involved in tasks such as transplanting, weeding and harvesting.” Female farmworkers are at high risk since DCPA has been shown to be toxic to the fetus producing lifelong health problems. The reader is invited to read the link for details in the toxicology. The successive degradation of DCPA is shown below. In addition to hydrolysis, it is also subject to photodegradation in sunlight.

Graphics by John Jacob Jingleheimer Schmidt.

Why wasn’t this discovered earlier? I’m not an EPA pesticide guy, but discovering the specific toxicity of herbicides registered many years previously requires some kind of trigger to get an investigation started. Today, other than an overt incidence of toxic effects making the news, that trigger can be the Registration Review Overview conducted by EPA every 15 years for each registered pesticide.

Having interacted with a certain division of the USEPA for the last 3 years, I can say that there are many intelligent and knowledgeable scientists, engineers and other professionals who try to get things done in a very constricted space bounded by layers upon layers of federal laws converted into regulations. They are about as loved as the Internal Revenue Service and, like IRS, are forced to work wildly understaffed and with an IT system that is decades out of date. A doff of the hat to EPA.

A Bit of Fentanyl Chemistry

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A recent raid on a clandestine drug lab in the Hatzic Valley east of Vancouver, BC, netted 25 kg of “pure” fentanyl and 3 kg which had already been cut for street use. Precursor chemicals used to manufacture the fentanyl were also seized. Along with the drug, the raid also seized 2,000 liters of chemicals and 6,000 liters (about 30 drums) of hazardous chemical waste, according to an RCMP news release 2 November, 2023.

The police said that the seizure represented 2,500,000 street doses.

In August of 2023 the police in Hamilton, Ontario, announced the results of Project Odeon. This was a large-scale sweep of illicit drug production in the Hamilton and Toronto area. From January 1, to July 30, 2023 there were 606 incidents related to suspected opioid overdoses and 89 suspected drug related deaths in the Hamilton area. Twelve people were charged for a total of 48 criminal charges. The police disclosed the following items that they seized-

  • An operational fentanyl drug lab at 6800 Sixteen Road, Smithville.
  • A dismantled fentanyl drug lab at 4057 Bethesda Road, Stouffville.
  • Approximately 3.5 tons of chemical byproduct from fentanyl production.
  • 800 gallons of chemicals commonly used in the production of fentanyl
  • Lab equipment commonly used in the production of fentanyl
  • 64.1 kg of illicit drugs, including 25.6 kg of fentanyl, 18 kg methamphetamine, 6 kg of ketamine
  • A loaded, Glock firearm and ammunition and four extended magazines
  • Over $350,000 of seized proceeds, including cars, jewelry, furniture and cash

Fentanyl is a synthetic drug first prepared in 1959 in Belgium by Paul Janssen (1926-2003). Janssen was the founder of Janssen Pharmaceuticals, now a subsidiary of Johnson & Johnson. In addition to fentanyl, the Jenssen team developed haloperidol, the ultrapotent carfentanil, and other piperidine based congeners. Piperidine itself is a DEA List 1 substance in the US.

Carfentanil is just modified fentanyl. Graphics: Will O. de Wisp

The elephant in the room with fentanyl is its extraordinary potency as an opioid. In pharmacology, potency is a quantitative measure of the amount of dose needed to elicit a specific effect on an animal or human in terms of dose weight per kilogram of body mass. Potency is subject to variability across a population and rises to an asymptote which can be difficult to pin down. For these reasons potency is reported at 50 %. For highly potent drugs like fentanyl, the measure is expressed as milligrams or micrograms of dose per kilogram body weight (mg/kg or mcg/kg body weight). One milligram per kilogram is one part per million (ppm).

When matters of toxicity arise, it is important to remember the maxim that “the dose makes the poison”. This observation traces back to Paracelsus in the mid-sixteenth century.

 “All things are poison, and nothing is without poison; the dosage alone makes it so a thing is not a poison.”

– Paracelsus, 1538. Source: Wikipedia

Fentanyl acts much like morphine in regard to its affinity for one particular opioid receptor. Morphine is commonly the “standard” with which other opioids are compared. For instance, fentanyl is said to be 50-100 times more potent than morphine. Only 0.1 mg of fentanyl is equivalent to 10 mg of morphine. Carfentanil is more potent still at 10,000 times the potency of morphine.

Morphine is an agonist which activates the μ-opioid receptor. Activation of this receptor with morphine produces analgesia, sedation, euphoria, decreased respiration and decreased bowel motility leading to the earthly delights of constipation. Fentanyl is thought to interact with this receptor as well.

Original fentanyl synthesis by Janssen. Graphics: Will O. de Wisp

So, how is fentanyl synthesized? See the synthetic scheme above. I’ll just comment on the Janssen synthesis and some issues. I have no idea of how it is made out in there by the Mexican cartels and in ramshackle American trailer parks. The synthesis above has some steps that may be undesirable for backwoods or jungle operations like hydrogenation. In the first step, aniline will be needed to make the phenyl imine. It’s pretty toxic and stinks to high heaven. Next, lithium aluminum hydride is needed to reduce the imine double bond to an amine. This innocent looking grey powder is very hazardous and should only be used by an experienced chemist. It is also available as a solution in tetrahydrofuran. The next step is the formation of the amide with propionic anhydride. While the reaction entails a simple reflux, you still have to isolate the product. Once you have recovered the amide, the benzyl protecting group on the piperidine nitrogen must be removed. It allowed amide formation exclusively on the upper aniline nitrogen and has served its purpose. Finally, the piperidine nitrogen must be festooned with a phenylethyl group and phenylethyl chloride was used to afford the fentanyl product. 

An excellent review of the pharmacology and drug design of this family of opioids, see Future Med Chem. 2014 Mar; 6(4): 385–412.

In chemical synthesis generally, substances are prepared in a stepwise manner and with as few high yielding steps as possible. To begin, one must devise a synthesis beginning with commercially available raw materials as close to the target as possible. If the product has many fragments hanging off the core structure, it’s best to solve that problem early. Synthetic chemistry is almost always performed in a non-interfering solvent that will dissolve the reactants and allow the necessary reaction to occur. A low boiling point is preferable for ease of distillation. An important side benefit from a solvent is that it will absorb much of the heat of reaction which can be considerable. Left on its own, a reaction might take its solvent to the boiling point by self-heating, generating pressure and vapor. The benefit from evaporation or reflux boiling is that as a solvent transitions from liquid to vapor there is a strong cooling effect which helps to control the temperature. An overhead condenser will return cooled solvent to prevent solvent loss.

You can do any chemical synthesis in one step with the right starting materials. Unfortunately, this option is rarely available. The next best option is to take commercially available starting materials through a known synthetic scheme. People who run illicit drug labs are never interested in R&D. They want (and need) simple chemistry that can be done by non-chemists in buckets or coke bottles at remote locations. Chemical glassware can be purchased but sometimes the authorities will be notified of a suspicious order. This is especially true with 12 liter round bottom flasks.

The most difficult and risky trick to illicit drug synthesis is obtaining starting materials like piperidine compounds in the case of fentanyl and its congeners. In the case of heroin, acetic anhydride shipments have been investigated for a long time because it is used to convert morphine to heroin- an unusually simple one-step conversion. Solvent diethyl ether is similarly difficult to get outside of established companies or universities. Many other common drug starting materials are difficult to obtain legally in the US or EU by the criminal element. However, China is thought to be a major supplier of starting materials outside the US and EU. Countries with remote coastlines, loose borders, lackadaisical or corrupt law enforcement reduce the barriers for entry of drug precursors. China in particular has a large number of chemical plants that make diverse precursors for legitimate drugs. Unfortunately, some of these precursors can also be used for illicit drugs or existing technology adapted for this use. Precursors can be sold to resellers who can do as they please with them. Agents may represent many manufacturers and can mask the manufacturer’s identity and take charge of the distribution abroad. Shady transactions become difficult for authorities to detect and trace. The identity of illicit precursor chemicals are easily altered in the paperwork to grease the skids through customs. Resellers can repackage chemicals to suitable scale, change the paperwork and jack up the price for export. It has been my experience that many if not most Chinese or Japanese chemical manufacturers conduct business through independent export agents. However, behind the curtains there often a byzantine web of connections between companies and agents, so you may never know who will manufacture your chemical. As an aside, this complicates getting technical information from the manufacturer since the agent will not disclose a contact at that manufacturer.

Highly potent drugs like fentanyl must be taken in very small dosages which means that kilo-scale batch quantities of drug result in many individual sales per kilo. Small quantities of highly potent drugs are more easily smuggled than bulky drugs like weed with its strong odor.

There is a down-side to the illicit manufacture of drugs like fentanyl. It is quite toxic at very low dosages and must be handled with the greatest of care lest the “cook” and other handlers get inadvertently and mortally poisoned. Good housekeeping helps, but I have yet to see a photo of a tidy drug lab.

Fentanyl can be sold as a single drug but perhaps is cut with a solid diluent that some random yayhoo decided was Ok to use. Other drugs of abuse like heroin may be surreptitiously spiked with fentanyl to kick up the potency. In either case, a given dosage may or may not be safe even for a single use. There is no way for a user to know. Also, the concentration or homogeneity of mixed solids may be subject to wide variation. For more than a few people, their first fentanyl dose will be their last.

Chemical Emergencies and Safety Data Sheets in Education

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Note: Below is a quick safety brain-dump from a career in academic chemistry labs and chemical manufacturing facilities. It is not meant to be an unabridged guide to lab safety. Look elsewhere for that. it is easy to overlook Safety Data Sheets that come with chemical purchases.

At some time in their chemistry education the student should have had a good look at the chemical Safety Data Sheet or SDS for the chemicals and solvents they are using. While not necessarily very informative in terms of reaction chemistry, these documents are taken very seriously by many groups who can/will have an impact on your chemistry career and safety. Regardless of your walking-around-knowledge about a chemical substance, you should understand that the people who respond to emergency calls for a chemical incident will place a high reliance on what is disclosed on an SDS. A student who is connected with an incident won’t be the first point of contact when the fire department or ambulance arrives and wants information. In fact, it is highly unlikely that a student will ever have direct contact with a responder unless it is with an EMT.

Know where the SDS folder is. It may be in print or online.

When emergency responders arrive at the scene of your chemical incident, they will have protocols built into a strict chain of command. All information will pass through the responder’s single point of contact. The fire fighter with the fire hose is not the person you should try to communicate with. Information regarding the incident must be communicated up the chain of command from your site incident commander. The person responsible for the lab should know who that is. The staff at the incident site (your college) will also have protocols built onto a chain of command. Again, “ideally” the incident commander at the incident site will ask for information from others on the site regarding details on the event including the headcount (!) and communicate it to the incident commander of the responders. This is done to avoid confusing the responders with contradictory or useless information. Do not flood the responders with extraneous information. Don’t speak in jargon. If there are important points like “it’s a potassium fire”, pass it along. If there are special hazards like compressed hydrogen cylinders present, they’d like to know that too. Answer their questions then step back and let them do their job.

When responders arrive at the scene of a chemical incident, the first question they will ask is if everyone is accounted for. If everyone is accounted for, they will not risk their lives in the emergency response. However, if there are people unaccounted for or known to be trapped in a dangerous place or incapacitated, the responders will take greater chances with their own safety to rescue the victims. They will act to minimize property damage only if it can be done without risk to life and limb. Nobody wants to die saving property.

College chemistry departments that I have been involved with have had a flat policy of evacuating everyone from the building and congregating them at a defined location in response to an alarm. That way there is at least some reasonable chance that an accurate head count can be made. If technical advice is needed, faculty connected with the incident site should be consulted. The college will have an Environmental Health and Safety (EH&S) group or person who presumably will take charge of the incident on the incident side. The leader of EH&S should be informed of any hazards unique to the substance of concern if there is no SDS. Let them communicate with the responders. Generally, we chemists help most when we keep out of the way.

College chemistry departments are famous for housing one-of-a-kind chemical substances in poorly labeled bottles in faculty labs. These substances almost never have any kind of safety information other than perhaps cautionary advice like “don’t get it in your eye.” Luckily, university research typically uses small quantities of most substances except perhaps for solvents. Solvents can easily be present at multiples of 20 liters. These large cans are properly kept in a flammables cabinet. While research quantities may not represent a large fire hazard initially, there could easily be enough to poison someone. When you get to the hospital, the ER folks will have to figure out what to do with your sorry ass lying there poisoned by your own one-of-a-kind hazardous material.

In principle, the professor in charge of a chemistry research lab should be responsible for keeping an inventory of all chemicals including research substances sitting on the shelf. Purchased chemicals always have an SDS shipped with them. These documents should be filed in a well-known location and available to EH&S and responders.

The chemistry stockroom is a special location. Chemicals are commonly present at what an academic might call “bulk” scale, namely 100 to 1000 grams for solids and numerous 20 L solvent cans. The number of kg of combustibles and flammables per square meter of floor space is higher here. The stockroom manager should have a collection of SDS documents on file available to responders.

Right or wrong, people positively correlate the degree of hazard to the nastiness of an odor. Emergency responders are no different. This is another reason why it is critical for them to have an SDS. People need to adjust their risk exposure to the hazard present as defined by an SDS. We all know that some substances that are bad actors actually have an odor that is not unpleasant for a short time, like phosgene. Regardless of this imperfect correlation, if you can smell it, you are getting it in you and this is to be avoided. Inhalation is an important route of exposure.

In grad school we had an incident where a grad student dropped a bottle in a stairwell (!) with a few grams of a transition group metal complex having a cyclooctadiene (COD) ligand on it. Enough COD was released into the stairwell to badly stink it up. They didn’t know if it was an actual chemical hazard or not, so they pulled the fire alarm handle. The Hazardous Material wagon showed up right next to 50-60 chemistry professors, postdocs, and grad students. The responders were told what happened and with what, so they dutifully tried to find information on the hazards in their many manuals. They did not find anything.

They had 50-60 chemists within spitting distance but didn’t ask us any questions. This is because they are trained to respond as they did. This was a one-off research sample of a few grams but it had an obnoxious smell with unknown hazards. Finally they sent in some guys in SCBA gear and swept up the several grams of substance and set up a fan for ventilation. Don’t be surprised if the responders don’t have special tricks up their sleeves for your chemical event. They can’t anticipate every kind of chemical incident.

HazMat Team. Credit: https://en.wikipedia.org/wiki/Hazardous_materials_apparatus

Long story short, both the responders and the chemists didn’t have any special techniques tailor made for this substance. There was not evident pyrophoricity or gas generation. It was a dry sample so no flammable liquids to contend with. The responders used maximum PPE and practiced good chemical hygiene in the small clean up. Case closed.

An SDS is required for shippers as well. It shows them how to placard their vehicles according to the hazards. Emergency responders need to see the SDS in order to safely respond to an overturned 18-wheeler in the road or to a spill on a loading dock. It could also be that the captain of container ship wants to know precisely what kind of hazardous materials are visiting his/her ship.

Finally, an SDS should be written by a professional trained to do it properly. By properly I mean by someone who understands enough about regulatory toxicology, emergency response, relevant physicochemical properties, hazard and precautionary statements and shipping regulations to provide responders with enough information to respond to an incident. Here, incident means an unexpected release with possible exposure to people, a release into the environment or a fire or possible explosion.

In my world, the word “accident” isn’t used so much anymore. With the advent process hazard analysis (PHA) required by OSHA under Process Safety Management prior to the startup of a process, potential hazards and dangers are anticipated by a group of experienced experts and adjusted for. So, it is getting harder to have an unexpected event. “Accident” is being replaced with the word “incident.”

Toxicology is a specialty concerned with poisons. Regulatory toxicology refers to the field where measurements and models are used to define where a substances belongs in the many layers of applicable regulations. Toxicity is manifested in many ways with many consequences and each way is categorized into levels of severity. There is acute toxicity and there is chronic toxicity. Know the difference. That said, dose and exposure are two different things. Exposure relates to the presence of external toxicants, i.e., ppm in water or micrograms per cubic meter of air. Dose relates to the amount of toxicant entering the body based on the exposure time in the presence of a toxicant and the route of entry.

An SDS uses signal words like “Caution”, Warning”, or “Danger”. A particular standard test is needed to narrow down the type and magnitude of the toxicity. The figure below from the GHS shows the thresholds for categorization of Acute Toxicity.

Credit: Globally Harmonized System of Classification and Labeling of Chemicals.

Hazard and precautionary statements are important for an SDS. Rather than having everybody dreaming up their own hazard descriptions and precautions, this has been standardized into agreed upon language. Among other sources, Sigma-Aldrich has a handy list of Hazard Statements and Precautionary Statements available online.

Regulatory toxicology is very much a quantitative science enmeshed with a web of regulations. The EPA for instance does modeling of human health and environmental risks based on quantitative exposure or release inputs. Without toxicological and industrial hygiene testing data, they may fall back on model substances and default, worst case inputs to their models. In reality the certain hazard warnings you see on an SDS may or may not be based on actual measurement. The EPA can require that certain hazard statements be put on a given SDS based on their assessment of risk using models or actual data.

To be clear, hazard information reported on an SDS are considered gospel to emergency responders. Chemists of all stripes should be conversant with Safety Data Sheets and have a look at them the next time a chemical arrives. Your lab or facility should have a central location for SDS documents, paper or electronic.

In the handling and storage of chemicals, some thought should be given as to how a non-chemist would deal with a chemical spill. Is the container labeled with a CAS number or a proper name rather than just a structure? A proper name or CAS # could lead someone to an SDS. Is there an HMIS or other hazard warning label? There are many tens of thousands of substances that are either a clear, colorless or amber liquid or a colorless solid. If not for the sake of emergency responders then for the poor sods in EH&S who will likely have to dispose of the stuff when you are long gone. Storing chemicals, liquids especially, with some kind of secondary containment is always a plus. Keep the number of kilograms of combustibles and flammables in the lab to a minimum. A localized fire is better than a fire that quickly spreads to the clutter on the benchtop or the floor.

The burnin’ ring of fire

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The Norfolk Southern train derailment and fire in East Palestine, OH, has spread into the political dumpster. By not appearing near the crash site promptly, both Biden and Buttigieg are feeling the heat of the GOP panic machine. The single plank on the GOP platform is to knock down Democrats at every opportunity. While the news organs of the GOP are busy trying to blame the Biden administration for the accident, fire and contamination, citizens are expressing dismay over not knowing what to do going forward. They aren’t receiving much advice or direction from EPA about how much they should be worried about contamination and exposure to the released chemicals. In fact, on the ground it has been hard to see the hand of government anywhere. Their frustration is normal and understandable. I would be frustrated too.

Let’s step back a minute and examine the situation from 50,000 ft. The last thing we want in government is for a proper response to an emergency of this scale to require the president to personally lead the emergency response. The same is true for the Secretary of Transportation. Good leaders delegate responsibility to specialists for situations like this. Good leaders are watchful but stay out of the way of the experts. Good leaders make sure that the people on the ground have the resources they need to do their jobs. Ok, Biden didn’t respond publicly to the situation early enough, but that is not to say that things weren’t happening. But, he has 330,000,000 American back-seat drivers to make happy. That’s his job.

Let’s remind ourselves that Biden and NATO are also busy trying to prevent the start of WWIII.

As with an emergency of any scale, it takes responders some time to understand the situation and then to bring resources to bear. In the mean time, the NTSB was promptly dispatched and has already published preliminary report RRD23MR005 on the event. It is very interesting to see that many of the safety systems worked. The overheated wheel was detected and an emergency braking procedure was put into action just before the derailment occurred.

Ok, Biden and Buttigieg could have been quicker to publicly extend sympathy and the promise of relief. Complaining about this is like accusing grandma of not giving you a kiss while she was trying to put out a fire in the kitchen. But contrast this PR error of omission with the antics of #45 in Puerto Rico after the recent hurricane. Remember how he tossed rolls of paper towels as mock support during an interview down there? MAGA people have no leg to stand on with presidential expressions of sympathy.

From Wikipedia, https://en.wikipedia.org/wiki/Dose%E2%80%93response_relationship

As far as what kind of toxic threat there is to humans and what potential environmental insult there will be, the situation has not fully played out yet. This will need to be studied for years. There is acute toxicity and there is chronic toxicity. With most chemicals there will be a clear dose-response relationship with chemical dosing if you choose the right experiment to do. However, that relationship can become quite uncertain with low dosing. The health effects of exposures from the East Palestine derailment cannot be measured with high precision over the long haul. Genuine toxic effects are over-printed on a background of natural disease. Diseased tissues do not have little signs that say “I was caused by vinyl chloride dosing”. Histology can characterize cell types and correlate them with known chemical insult, but only a jury can say if any particular conclusion will hold up in court. With toxicity effects, certainty is not always what you get.

Paracelsus said in 1538 that “All things are poison, and nothing is without poison; the dosage alone makes it so a thing is not a poison“. That observation is still true today.

Hazardous Metaphor On Fire in Ohio

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When I think “train wreck” I usually think of #45’s presidency. But here I refer to the actual Feb 3, 2023, Norfolk Southern train wreck in East Palestine, OH. A very long train carrying, among other things, tankers of hazardous chemicals had a derailment and fire near the small town of East Palestine, OH, along the southwest Pennsylvania border. It was a true calamity releasing hazardous chemicals, some of which caught fire and burned for days. It isn’t clear as yet as to what burned and what didn’t. The extent of pollution will eventually be released by authorities and monitored for years to come.

Early reports have claimed that the accident started with an overheated wheel bearing. It would be interesting learn how this could lead to a derailment. The root cause analysis will be interesting.

According to Wikipedia–

NTSB chair Jennifer Homendy explained that the train in this accident would not have been required to utilize the ECP braking system even if the FAST Act was not repealed, because the term high-hazard flammable train means a single train transporting 20 or more tank cars loaded with a Class 3 flammable liquid. As it had only three such placarded train cars, the derailed train did not meet the qualifications of a “high-hazard flammable” train.

ECP stands for Electronically Controlled Pneumatic brakes. The Wikipedia page describes the pathetic political kerfuffle over these brakes and how certain groups fought the requirements for them.

Photo from Wikipedia, https://en.wikipedia.org/wiki/2023_Ohio_train_derailment

The Washington Post released a piece, dated Feb 18, 2023, about it showing some interesting pictures. One aerial shot captures the wreckage along with what the cars were carrying. A security camera caught the train moving along with a large fire blazing under one car minutes before entering town. The video has since been removed.

The burning vinyl chloride (and … ?) produced a toxic plume that by some accounts was also corrosive. I assume this to be due to the burning of an organic chloride releasing hydrochloric acid vapors. According to Wikipedia, of the 150 cars in the train some 38 train cars were derailed.

Substances in cars that were derailed according to the Washington Post-

  • Vinyl chloride
  • Polyethylene
  • Dipropylene and propylene alcohol
  • Semolina (a wheat flour)
  • Polyvinyl chloride (PVC)
  • Ethylhexyl acrylate
  • Petroleum lubricating oil
  • Diethylene glycol
  • Isobutylene
  • Butyl acrylate
  • Benzene

Much was made in the news about burning vinyl chloride and noxious fumes, but I haven’t heard an accounting of what actually burned. Any release of acrylate monomers is especially unfortunate since as a group, they can be nasty lachrymators. This will take years to get through the courts.

Lost Capsule of Cs-137 Recovered in Western Australia

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According to Reuters, a 6 mm diameter by 8 mm long capsule of radioactive Cesium-137 was lost along the 1400 km road between a storage facility in suburban Perth and Rio Tinto’s Gudai-Darri iron mine in the Kimberley region of western Australia. The source was lost sometime between January 12 and the 25th, 2023. The capsule had been attached to a piece of equipment in a crate but evidently vibrated loose in transport from a road train– a multi-trailer vehicle- and fell off. While the activity was not disclosed the source was described as one that “emits radiation equal to 10 X-rays per hour”.

On February 1, 2023, the source was reportedly located after a week-long search along the 1400 km road. It was discovered by a vehicle moving at 70 kph with special detection equipment.