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Protection from Ortho-Toluidine - Part I

The current permissible occupational exposure limit in the United States for ortho-toluidine does not protect exposed workers from developing cancer.

The ortho-toluidine permissible exposure limit of 5 parts per million (ppm) was adopted by OSHA in 1971 from a threshold limit value (TLV) set by a voluntary association called the American Conference of Governmental Industrial Hygienists (ACGIH).  The 5 ppm TLV was based on research last conducted in the 1960's and carcinogenicity was never considered by the ACGIH.


Compliance with the 5 ppm OSHA standard is determined by taking an air sample in a worker’s breathing zone, even though absorption of the chemical through the skin is a major route of exposure.  Air sampling does not measure absorption of ortho-toluidine through the skin.  Thus, air sampling always results in an under-estimate of true exposure.


Urine sampling for ortho-toluidine can measure exposure from both inhalation and skin absorption.  DuPont, which manufactured ortho-toluidine from 1919 to 1995, was well-aware of this fact. From at least 1951, DuPont always relied upon urine sampling to protect its employees from the hazards of ortho-toluidine, but never provided this advice in its material safety data sheets (MSDS) to its customers and their exposed workers. 


NIOSH reported its first epidemiological study of the Goodyear plant in Niagara Falls, New York in December 1989.

There were 14 cases of bladder cancer observed and 3.54 expected based on New York State incidence rates among the 1749 individuals ever employed at the plant. The ratio of observed to expected cases (also known as the Standardized Risk Ratio or SIR) of 3.95 was found to be highly statistically significant (p=0.00002) indicating that this risk was very unlikely to have occurred by chance. There were 8 cases observed and 1.20 (SIR=6.64; p=0.00004) expected among 795 workers ever employed in an area of the plant where workers were definitely exposed to o-toluidine.                     


In that same study, NIOSH also reported "that worker exposure monitoring data that Goodyear industrial hygiene staff have collected since 1982 show that air concentrations of all chemicals present in Department 245 have been consistently less than one part per million (ppm)."


Department 245 was the area of the plant where ortho-toluidine was used. The NIOSH investigators also performed their own air sampling in the plant and confirmed that “the results for all the area air samples collected were less than 1 ppm.”  Id.  Thus, since 1989, it has been self-evident that the 5 ppm OSHA standard was not protective of workers’ health.

In 1990, NIOSH conducted an industrial hygiene study of the Goodyear plant.  In that study, for the first time, urine samples were taken from the Goodyear workers, both before the work-shift and after the work-shift, and the results were compared in order to determine their ortho-toluidine exposure.  


In a 1992 report on its 1990 study, NIOSH reported that the highest post-shift urinary ortho-toluidine level in the Goodyear workers was 527 micrograms of ortho-toluidine per liter of urine.  Id. at 67.  NIOSH stated: “This provides conclusive evidence that Department 245 workers were absorbing o-toluidine. . .into their bodies during the workshift.”  Id. at 2.

By April 20, 1993, DuPont scientists had determined that exposure to ortho-toluidine at the OSHA permissible exposure limit of 5 ppm for an 8 hour day would result in an ortho-toluidine concentration in the urine of 20 milligrams per liter.  Id. at KDH01094.

Thus by 1993, DuPont knew that worker exposure at the OSHA permissible exposure limit of 5 ppm for an 8-hour day would produce a urinary concentration of 20 milligrams per liter, which was 37 times higher than the highest level found in the Goodyear workers, whose risk for bladder cancer was greater than 6-fold (527 micrograms per liter is the same as .527 milligrams per liter; dividing 20 milligrams by .527 equals 37.95).


In 1976, the United States Congress passed the Toxic Substances Control Act (TSCA), 15 U.S.C. § 2601.  One of its purposes is “to regulate chemical substances and mixtures which present an unreasonable risk of injury to health and the environment, and to take action with respect to chemical substances and mixtures which are imminent hazards.”  Sec. 2(b)(2).


Section 8(e) of the Toxic Substances Control Act requires a chemical manufacturer to report to the EPA if it finds out something new about a chemical which might pose a substantial risk to human health. TSCA Section 8(e) provides:


    (e)     Notice to Administrator of substantial risks


Any person who manufactures, processes, or distributes in commerce a chemical substance or mixture and who obtains information which reasonably supports the conclusion that such substance or mixture presents a substantial risk of injury to health or the environment shall immediately inform the Administrator of such information unless such person has actual knowledge that the Administrator has been adequately informed of such information.


15 U.S.C. §  2607(e).  The EPA sees this provision as a critically important information gathering tool that serves as an “early warning” mechanism for keeping the Agency and others apprised of newly-found serious chemical hazards or exposures.


However, DuPont never notified the U. S. Environmental Protection Agency of its significant finding regarding ortho-toluidine in 1993 or at any later time.  Moreover, all DuPont material safety data sheets for ortho-toluidine issued after April 20, 1993 continued to list the 5 ppm OSHA PEL as an “exposure limit” and “exposure guideline,” without any warning as to the amount of ortho-toluidine that such exposure would produce in the urine, and thus exposing the bladder tissue to a known carcinogen. 


In a February 2, 1995 submission to the USEPA under TSCA Section 8(e), DuPont compounded its error and falsely represented to the agency that: “Based on all available toxicity data. . .the existing worker exposure limit (Acceptable Exposure Limit, AEL) was reviewed and its validity at 5 ppm, 8- and 12-hr. time weighted average, confirmed.” 
On January 4, 2021, I gave notice to the EPA of these facts and of my intent to proceed with a “Citizen’s Civil Action” against DuPont under Section 20 of the Toxic Substances Control Act.  This section of the statute permits any citizen to file an action in order to restrain a wrongdoer from a further violation of the TSCA.

Testimony of DuPont industrial hygienist Thomas J. Nelson:

    Q.     So here you're saying that if you are exposed for 5 parts per million inhalation over a day, you're going to end up with an OT urine level of 20 milligrams per liter; right?

    A.     Yes.

Testimony of DuPont’s global industrial hygienist Barbara J. Dawson:

   Q.     So if I do the math correctly, a 5 part per million exposure for 8 hours a day would produce a urinary concentration some 37 times higher than what was found in the Goodyear workers.  Correct?

    A.      That's what it says.

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