Questionable risk decisions under ChAMP: Chlorobenzenes Category

Cal Baier-Anderson, Ph.D., is a Health Scientist and Richard Denison, Ph.D., is a Senior Scientist.

Our analysis of EPA’s risk decision under ChAMP for this category of toxic chemicals vividly illustrates how EPA has failed to adopt a health-protective approach to its screening of HPV chemicals.  Rather, it misclassifies or understates these chemicals’ hazards, asserts that existing regulations are sufficient even when they are quite old or do not cover identified exposures, and naively assumes that children will not be as exposed as adults to consumer products used in the home unless they are intended for their use.  Finally, this case demonstrates that manufacturers are not reporting to EPA even readily available information on their chemicals’ uses. 

The chlorobenzenes category is comprised of four chemicals: monochlorobenzene (CAS# 108-90-7), 1,2-dichlorobenzene (CAS# 95-50-1), 1,3-dichlorobenzene (CAS# 541-73-1) and 1,2,3-trichlorobenzene (CAS# 87-61-6).  The first three of these chemicals are on the Toxics Release Inventory (TRI).  Reported production volumes under the Inventory Update Rule and TRI emissions for 2005 and reporting manufacturers (other companies may have claimed their identity to be confidential business information) for these chemicals are as follows:

Industrial uses reported by manufacturers include use as intermediates and solvents for plastics manufacturing and basic organic chemicals manufacturing, and pesticide and other agricultural chemical manufacturing.  EPA notes other uses cited in the Hazardous Substances Data Bank (HSDB):  “pesticides, solvents, heat transfer medium, and chemical intermediates, as well as many other uses.”

All members of this category were included in test rules issued under TSCA Section 4, in use and exposure-related information reporting rules issued under TSCA section 8(a), and health and safety data reporting rules issued under TSCA section 8(d).  Additionally, these chemicals are regulated under the Clean Air Act and Clean Water Act, and the Occupational Safety and Health Administration (OSHA) has set Permissible Exposure Limits (PELs) for two of the chemicals (1,2-dichlorobenzene and monochlorobenzene).

EPA considers 1,3-dichlorobenzene to be a high-priority chemical, a decision with which we agree (but see point 8 below).  It considers the other chemicals to be low-priority, and this review primarily focuses on that decision.

Hazard rankings:  EPA ranks monochlorobenzene, 1,2-dichlorobenzene and 1,2,3-trichlorobenzene as having moderate human health hazard, based on the results of repeated dose toxicity tests and developmental toxicity tests.  All three of these chemicals (as well as 1,3-dichlorobenzene and one of the supporting chemicals for the category) exhibited evidence of genotoxicity in vivo. One of the chemicals (monochlorobenzene) exhibited some, though not clear, evidence of carcinogenicity, and one of the supporting chemicals showed clear evidence of carcinogenicity.

Exposure rankings:  EPA indicates that there is a high potential for exposure to these chemicals of the general public via environmental releases, based on their reported TRI releases, environmental persistence, detection in environmental monitoring and their myriad uses.  EPA ranks worker exposures high (for two chemicals) and moderate (for the third).  Based on the use of these chemicals in consumer products, EPA ranks exposures to consumers as high and exposures to children as medium.  Interestingly, EPA reports that the IUR data – submitted by manufacturers – do not indicate uses in consumer products, but that several other sources, including the HSDB, the NIH Household Products Database, and EPA’s Source Ranking Database, do indicate uses in consumer products.

Risk rankings:  EPA ranks the risks of these three chemicals to the environment to be moderate to fish and high to invertebrates and aquatic plants.  It ranks risks to the general public, consumer and children as moderate, despite their high exposure potential, based on ranking human health hazard as moderate.  EPA ranks risks to workers as low for the two chemicals with OSHA PELs (1,2-dichlorobenzene and monochlorobenzene) and moderate for 1,2,3-trichlorobenzene.

Prioritization rankings:  EPA considers all three chemicals to be low-priority because it expects existing regulations and ongoing reporting to be sufficient to mitigate risk and to alert EPA to the presence of chemicals in workplaces, environmental releases from facilities, and drinking water.

Why we disagree:

1. Given the high exposure potential to these chemicals, which EPA found to pose moderate human health hazards, even a modestly health-protective decision would rank their risks to the general public, consumers and children as high, not moderate. The potentially large number of uses, the large production volumes and TRI releases for two of the three chemicals and the substantial uncertainty regarding the magnitude, frequency, and duration of possible exposures, would support such a ranking.
   In this way, at least the development of better hazard, use and exposure information and further scrutiny of the magnitude of risks would be spurred.  Instead, EPA concludes that “No follow-up action is suggested at this time on [these three] chemicals in this category.
2. The conclusion that these chemicals are low-priority due to the existence of Clean Air Act and Clean Water Act regulations is unjustified. Despite those regulations, substantial TRI releases to air and some releases to water are being reported – sufficient for EPA to rank exposure potential as high. Yet EPA then invokes those same regulations as being adequate to prevent the very exposures it just characterized as potentially high!
3. The main reason EPA ranked consumers’ and children’s exposure potential high and medium, respectively, is because of expected exposures through consumer products. However, the cited CAA and CWA regulations do not address these exposures at all.
4. EPA provides no real basis for ranking children’s risks lower than consumers’. EPA implies this is because it lacks evidence that these chemicals are used in products specifically intended for use by children. But EPA notes it sources of use information indicate “many other uses” for these chemicals that are not identified, and EPA provides no basis on which to conclude that uses in products not intended for use by children would not expose them. Indeed, EPA acknowledges: “Exposures to children, however, may be expected to occur through the household use of some consumer products” (p. 48 here).
5. Positive results for all of the chemicals in this category in in vivo genotoxicity studies, and for monochlorobenzene and one of the supporting chemicals in two-year carcinogenicity bioassays, clearly warrant follow-on testing to clarify the carcinogenic potential of at least the untested chemicals in this category. Yet EPA proposes no such testing; indeed it barely discusses the findings other than to repeatedly emphasize the one chemical for which negative carcinogenicity results were found.
6. In its risk rationale for children, EPA misclassifies the level of developmental toxicity for two of the three chemicals. On p. 3 here, EPA claims “available data with postnatal exposures in animals suggest a low hazard for two category members (CASRNs 95-50-1 and 108-90-7).” Yet the results of developmental toxicity tests in rats via inhalation exposure to vapors of these two chemicals actually showed moderate and high developmental toxicity, respectively, based on EPA’s own criteria:
   • CAS# 95-50-1:  LOAEL ~ 2.4 mg/L/day vs. EPA range for moderate developmental toxicity of 1-2.5 mg/L/day (see pp. 27 and 38 here vs. the table on p. 12 of EPA’s Methodology for Risk-Based Prioritizations under ChAMP.
   • CAS# 108-90-7:  LOAEL ~ 0.35 mg/L/day vs. EPA cutoff for high developmental toxicity of <1.0 mg/L/day (see pp. 26 and 38 here vs. the table on p. 12 of EPA’s Methodology for Risk-Based Prioritizations under ChAMP
     High exposure and high or moderate developmental toxicity – surely even EPA will acknowledge these chemicals merit a high-risk and high-priority ranking?
7. EPA invokes the existence of OSHA PELs for two of these chemicals to argue that worker risk is low. Both of these PELs were promulgated in 1989 (see here and here), and at least for one of them, monochlorobenzene, NIOSH has found that “[t]he 1989 OSHA PEL may not be protective to workers.”
        Were these PELs developed in consideration of and are they adequate to protect against the toxicities EPA presents herein?  While some of the test data (ca. 1984, 1987) predate the year the PELs were adopted, given the long process required to develop a PEL, the timing cannot be taken as evidence that such data were considered by OSHA.  EPA cannot merely assert that the PELs are adequate to protect workers without demonstrating that the permissible levels were set after evaluation of these data, and are still adequate in light of any other more recent toxicity data.
   At the very least, EPA needs to engage in a meaningful referral of these data to OSHA, using its TSCA Section 9 authority, including follow-up to ensure the data have been fully considered and acted upon appropriately at OSHA.
8. Despite its high-priority finding for one of the chemicals in this category, 1,3-dichlorobenzene, EPA’s only response is to state that “in order to confirm or refute the high potential risk … companies are encouraged to provide available information on a voluntary and non-confidential basis.” This is clearly inadequate for such a high-risk chemical. It begs the question: what would it take for EPA to be willing to actually impose risk management on such a chemical?
9. Last but not least, EPA’s finding that there are myriad product uses of these chemicals – none of which were reported by any of their manufacturers under the Inventory Update Rule (IUR) – vividly illustrates why EPA’s frequent sole or primary reliance on the IUR as its source of use and exposure data for ChAMP assessments is wholly inadequate as a basis for making exposure and risk decisions for high production volume chemicals.