Managing Aggressive Solvents – Point/Counterpoint

Barb Kanegsberg with Kevin Pawlowski*

As indicated in a recent LinkedIn post (Ref 1), perchloroethylene “creeps” – it has favorable wetting properties that allow access to residue in tight spaces. Many classic chlorinated and brominated solvents have similar “creeping” or wetting properties; and they have aggressive solvency properties – they are effective in removing soils. These solvents are under heavy regulatory pressure by the EPA. While rules are at various stages of development, at this point it appears that many uses may be banned and that where they are allowed, there will be restrictions/requirements including containment, monitoring, and reporting.

Barbara added a comment in LinkedIn about allowing such solvents to be used in well-contained systems. Our friend and colleague, Kevin Pawlowski, countered with a different viewpoint. We think it’s important to look at chemicals management from different perspectives, so we expanded the dialogue from both our and Kevin’s perspectives. Read on for educational point/counterpoint ideas.

Barbara’s comments on LinkedIn:

All product manufacturers involved in surface preparation and critical cleaning – and all people involved in safety/environmental regulatory activities – must read this post about the value of Perchloroethylene in achieving effective residue removal. Trichloroethylene, n-propyl bromide, and methylene chloride have similar favorable properties (higher density, lower surface tension, lower viscosity). Because such solvents “creep,” they do the job of removing soils in certain instances where substitutes are not as effective. They can be used safely with minimal employee exposure. Manufactured products need to be cleaned effectively. Demonizing and banning effective cleaning solvents is a popular notion; but it is a dreadful, dangerous trend that adversely impacts public safety and patient safety. Instead, we need to grow a culture where ALL chemicals are managed carefully. The correct chemical, used properly, may be the “green” approach.

Kevin’s response on LinkedIn:

“Used properly” is the key word. It’s hard for me to disagree with that statement, but on the other hand, heavy industry has a dark history of self-regulating such things.

If these solvents remain legal and readily available, it seems reasonable that more stringent reporting and auditing standards (I.e. EPA and OSHA) are put in place and paid for by the user. That has the added benefit of closing the cost gap between these lower-cost chlorinated and brominated solvents and alternatives, encouraging the use of “safer” alternatives when benefits like “creep’ aren’t needed.

Barbara and Kevin added additional comments for this article. 

Barbara: I see your point, Kevin. However, I don’t think the “dark history” is restricted to heavy industry. There are “bad actors” in every field. Many if not most manufacturers strive to comply with the rules. Many of them have used n-propyl bromide not only because of the cost but also because it was not listed as a Hazardous Air Pollutant (HAP) and therefore could legally be used in more emissive non-NESHAP compliant vapor degreasers, Perhaps EPA could have taken more expeditious steps to include nPB among the HAPS. Further, regulatory pressures have impelled chemical suppliers to make business decisions that impact chemical availability. A major supplier of trichloroethylene (TCE) ceased U.S. production. Faced with shortages, some industrial manufacturing companies who need to clean product reportedly moved from TCE to nPB to maintain quality production. Did the move from TCE to nPB impact what we think of as “safety/critical” applications? Could such changes impact public or patient safety? I hope not! nPB is similar in structure, chemical, and physical properties to TCE. So, the cleaning and materials compatibility performance would be expected to be similar. However, what if product manufacturers were pressured to move to other chemicals and processes with properties that are very dissimilar to the aggressive halogenated solvents? It is logical that the risk to product performance will increase. To minimize the risk, testing of the alternative chemicals for the specific application becomes essential. The availability of testing facilities where new processes can be evaluated is important. Test facilities are limited. Many manufacturers doing critical cleaning may not do adequate testing of the new process. Product manufacturers with fewer resources or companies with intractable company policies regarding what chemicals cannot be used are more likely to quickly switch to processes that often simply do not work adequately.

Kevin: We actually don’t seem very far apart on a few points:

  1. TCE, perc, and nPB are all great cleaners with unique and useful properties. 
  2. Outright bans have unintended consequences that can be counterproductive. Case in point, the ban on ozone depleters has certainly increased the usage of global warmers. The folks writing the regulations aren’t always experts, and sometimes have ulterior motives.
  3. It is possible to control emissions of toxic solvents to a very high degree given the will and budget.

There could well be some applications that require access to solvents like perc simply for the cleaning performance, and other solvents simply don’t penetrate or solvate adequately. In those cases, the onus is stil on the user to follow exposure guidelines to make sure working conditions are safe. Whether or not those emission controls make the process costly is beside the point. That is simply the necessary cost of doing business.

On the other hand, from what I’ve seen in the field, the vast majority of manufacturers using these solvents are doing so because of cost advantages (cost of material, and to avoid the cost of switching), not because of special properties. Those that actually need perc for its high boiling point (e.g. removing waxy soils) or creep (cleaning small machined holes) are outliers. 

Unfortunately, that same cost consciousness can lead many manufacturers to cut corners when it comes to emission controls. Certainly a $10B organization with a dedicated H&S departments should have controls well in hand, but what about the hundreds of smaller mom & pop shops? 

Barbara: It appears that many of the rules emanating from “amended TSCA” will have at best a 10-year exemption for certain applications. That puts a cap on usage; and there are expensive equipment, monitoring, and reporting requirements. Requiring the product manufacturer to pay the costs of solvent containment and reporting is punitive, unjustified, and unrealistic. Many solvent substitutes are flammable or combustible and must be used in appropriately designed cleaning machines. Purchasing such systems involves a substantial capital investment. 

Kevin: There is no doubt that bringing equipment up to emission standards or changing your process to work with a different class of solvents all takes money. Alcohols are generally inexpensive, but they like to blow up, so controls need to be in place. It is the manufacturer’s responsibility to incur the cost of keeping their employees safe – period. Once the data is clear what those controls need to be (i.e. toxicity, flammability), regulations need to be set and enforced to ensure employee safety. 

Barbara: Analogous to the old parable of “the carrot and the stick”, many current and impending regulations have a large stick and no carrot. Equipment costs are high; process evaluation costs are higher. Further, the impending regulations do not appear to define or recognize what Ed and I refer to as sealed, reduced pressure cleaning machines (2). Such systems ought to be defined by regulatory agents; and their use should be encouraged. The carrot in encouragement means, to me, nation-wide incentives to manufacturers to adopt such systems and perhaps programs for equipment designers to develop smaller, more cost-effective systems. Current systems can cost hundreds of thousands of dollars, even for small cleaning machines. This is beyond the financial reach of many companies.

One likely consequence is the increasing decline of U.S. manufacturing and the growth of manufacturing in other parts of the globe. Companies may inevitably make the economic decision to move. We saw the trend starting in the 1990s with the effort to eliminate ozone depleting compounds. Some large corporations publicly asserted that they support EPA regulations; and, while the regulations were not the only factor, they proceeded to move many facilities offshore. The actions of large companies have a ripple effect on smaller ones. Exporting air pollution or water pollution is not the answer. No matter where industry is operating on planet Earth, I’m sure no one wants to see workers or nearby people exposed to high levels of any process chemicals. 

Kevin: Once we have high confidence of the dangers of a solvent, we all should be duty-bound to reduce exposure to workers. For example, per ACGIH, perc has a TWA (time weighted average) of 25ppm, and nPB 1/10th of a PPM. An average manufacturer would be hard-pressed to keep exposure reliably below 50ppm. Without stringent regulations, the full impact of that excess exposure falls on the employee, not the employer. Now tell me, who is better able to bear that kind of cost? 

Is there a risk of manufacturing leaving the US due to these additional costs? Absolutely. That shouldn’t stop us from protecting our own citizens. Revised requirements for worker safety (granted hard to enforce) could be included in import regulations, as we do on conflict metals (section 1502 of the Dodd Frank Act). 

Barbara: Further, by taking a chemical-by-chemical approach and by demonizing well-studied chemicals, regulatory agencies effectively force manufacturers toward chemicals that are not as well studied as well as toward complex cleaning agent blends (solvent based and water based) that may have undesirable additive or synergistic impacts We do not know all we need to about such products, they are more likely to be used in ways that could adversely impact air, water, employees, and neighborhoods. I don’t think industry is trying to be evil; more often, they are trying to survive and to obey an assortment of complex, every-changing, sometimes contradictory regulations. As we’ve seen over many years, the “safer” chemical of today may well become the “evil” chemical of tomorrow. Perhaps we need a more encompassing approach, one that has a healthy degree of fear of all process chemical, especially those where there is very little toxicological information. I visit facilities that use all manner of chemicals, including cleaning agents, metalworking fluids, and other process fluids. Even with aqueous processes, too often my eyes water, my throat tickles, and my hair curls up (more than what could be attributed to high humidity). These processes are often not well-regulated. Cleaning processes ought to be adequately controlled and contained. Perhaps a limited version of the precautionary principle would be better environmental policy. That said, compliance costs should not be foisted on manufacturers. 

Kevin: I don’t see an alternative to the chemical-by-chemical approach. There is no denying some chemicals are more toxic than others, so varying the controls only makes sense. Exposure and emissions need to be controlled within prescribed limits, and if that isn’t practical, then we are left with bans. 

Barbara: I. have grave concerns about the EPA employee exposure limits. The ECEL (Existing Chemical Exposure Limit) for the chemicals under regulatory scrutiny are far, far lower than those developed by OSHA, CAL/OSHA, and ACGIH. (3). While these numbers might possibly change in the final rules, at this point they are breath-takingly low. For example, the ECEL for TCE is 0.004 ppm as compared with the CAL/OSHA PEL of 10 ppm. Really? It is possible to measure the exposure numbers using very long sampling times, “Sealed, reduced pressure” (airless systems) can lower chemicals emissions dramatically. That said, the rationale for the ECELs is not clear or compelling to me, Based on my limited perusal of the EPA reports, it appears that the EPA has used exposure observations from select animal studies, then divided by what the writers deemed to be an appropriate safety factor. I am not able to spend the time to read every word in the four reports, let alone to track down every study listed in the pages and pages of references. Given the amount of time these solvents have been in use, I would expect there to be direct, compelling evidence of health problems with workers and neighbors exposed to these chemicals. As some of my Industrial Hygiene buddies might say: “Where are the dead bodies?” Many proposed alternative chemicals have not been studied as extensively. I would expect that given enough studies on animals it would be possible to rationalize very, very low allowable exposure numbers for many chemicals that are not currently considered to be “bad.” 

Kevin: I don’t believe manufactures want to put their workers in harm’s way, but that can be the result of their choices. More times than not, these choices have a profit motive, so in a capitalist society, controls sometimes have to be put in place. While demonizing a chemical isn’t the answer, requiring emission and exposure controls to within safe limits seems prudent. If those limits are unrealistic for the majority of users, either the government needs to spend a lot of resources policing to keep those in check (moving to the “who will pay for it” discussion) or an outright ban for practicality sake.

Middle ground could be restricting the use of such chemicals to specific applications where the unique properties are required. The onus would be on the manufacturer to register the application and get approval. Everyone else would have to find an alternative – cost be damned. 

What’s next?
Kevin and I have different viewpoints. Neither of us is Ruler of the World (or even of the U.S.) We hope our comments promote more interchange, more ideas to promote sustainable, profitable manufacturing. Let’s talk about it!

Thanks to Ed Kanegsberg for reviewing and moderating this article.


  1. Linkedin post, SAFECHEM, “creeping abilities” and PCE
  2. B. Kanegsberg and E. Kanegsberg, “Degreasers,” Clean Source, January 2024
  3. B. Kanegsberg and E. Kanegsberg, “Degreasing and Fireworks,” Clean Source, July, 2022, (July 2022)

Additional resources

B. Kanegsberg and E. Kanegsberg, “Wettability and Solvency,” Clean Source, October 2022, (Oct. 2022)

B. Kanegsberg and E. Kanegsberg, Chemophobia,” Clean Source, May 2023 

*About Kevin:
Kevin Pawlowski has been marketing solvent replacements for nPB, TCE, perc, and methylene chloride for over 20 years, and has written many papers and hosted several webinars on the topic of “safer” solvents. 

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