Draft assessments for five chemicals

Five widely used high-production volume chemicals–including two of the best known and most regulated industrial solvents–comprise EPA’s first draft risk assessments under the Agency’s 2012 Toxic Substances Control Act (TSCA) Work Plan.  The intent of the Work Plan is to determine the risks 83 chemicals pose to human health and the environment.   The Work Plan was developed under the leadership of outgoing EPA Administrator Lisa Jackson, who ranked controlling chemical risk high among the Agency’s annual priorities.  This is a policy that the EPA undertakes at its discretion, and there are no assurances that the new administrator will continue the program. 

The risks from the five chemicals were examined in the context of specific uses.  For example, in the United States, 85 percent of trichloroethylene (TCE) is used as a chemical intermediate in the production of refrigerant chemicals.  That use occurs in closed systems that do not typically result in exposure to people.  But almost all the remaining TCE is used for metals degreasing, which does not normally involve enclosed systems.  The EPA has also found that human exposure to TCE during degreasing is typically not a major concern at large facilities that control emissions and provide workers with personal protective equipment.  That is often not the case at smaller facilities such as auto repair shops.

Therefore, the draft assessment focuses primarily on exposure to workers that use TCE to degrease metals in small facilities.  The exposure to “bystanders,” or those who are not using the product but are close enough to it to be exposed, is included in the assessment.  For TCE, the draft assessment relied on a variety of sources to estimate exposure, including the Toxics Release Inventory and the National Emissions Inventory. 

The five draft assessments also summarize hazard information–or the risk of illness presented by exposure.  The EPA drew this information from many sources, including U.S. government research, academic studies, and international research, particularly information developed in the European Union (EU).  The EPA also made extensive use of toxicological reviews completed as part of the Agency’s Integrated Risk Information System (IRIS), a program that evaluates information on health effects that may result from exposure to environmental contaminants.

Some of the draft assessments address risks to species while others do not, including the assessment for TCE, which has a low bioaccumulation potential.  On the other hand, the assessment for 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8,-hexamethylcyclopenta[g]-2-benzopyran (HHCB), a fragrance included in many personal care and household products, is directed almost exclusively at risks posed to aquatic organisms because the current knowledge indicates negligible health risks to humans.

Existing chemicals

What does all this mean to the regulated community?  Mainly, the Work Plan is the Agency’s latest effort to exercise its very limited statutory authority to regulate existing chemicals.  For example, under TSCA Section 6, the Agency can take numerous actions (including prohibiting manufacture) to reduce the risk from an existing chemical.  However, the Agency must first establish that the chemical presents an unreasonable risk.  This has proved to be an almost unscalable legal mountain for the EPA in the 36 years of TSCA’s existence. 

The same situation exists with TSCA Section 4, which authorizes the EPA to require manufacturers to subject existing chemicals to testing; but, again, this can only be done after the Agency shows that the chemical presents unreasonable risks.  In other words, testing for risks can be required only after the Agency establishes that the chemical presents risks–a classic catch-22 in the opinion of TSCA critics. 

The EPA has slightly more authority over existing chemicals that are put to new uses.  TSCA Section 5 requires that manufacturers (which by definition includes importers) that want to use an existing chemical in a new way notify the Agency in advance of that action.  After reviewing the data, the Agency has the opportunity to regulate the new use; but once again, to do so the Agency must establish unreasonable risk.

Despite many calls to reform TSCA, including bills in Congress and recent endorsements for reform from the chemical industry itself, the nation is still stuck with the same law.  The draft assessments constitute EPA’s attempt to use the latest science to demonstrate that the risks from some existing chemicals are sufficient to activate the TSCA existing chemical authorities in ways that will not be summarily thrown out in a court of law.  Should the final assessments fail to result in additional regulation of existing chemicals, the Agency and those calling for reform may use those failures as a further demonstration that the existing law is virtually useless as a tool to reduce the risks from existing chemicals.

Following major points are included in EPA’s five draft risk assessments.

TCE

The U.S. produces or imports about 250 million pounds of TCE annually.  Because of its large production volume, high volatility, and history of releases to all environmental media, the chemical is regulated under multiple EPA programs covering air emissions, hazardous waste, emergency response, water pollution, and toxic substances. 

According to the EPA, TCE is carcinogenic to humans based on “convincing evidence” of a causal relationship between TCE exposure in humans and kidney cancer.   Due to TCE’s high volatility, the Agency evaluated the inhalation exposure pathway only.  The potential for environmental effects was judged to be low because of TCE’s moderate persistence, low bioaccumulation, and low hazard for aquatic toxicity.

For the commercial degreaser user and nonuser, the assessment identified potential risks of concern for acute developmental toxicity and neurotoxicity effects and chronic effects for the liver, kidney, and immune systems.  For the hobbyist degreaser user and nonuser and for hobbyist clear protective spray users, potential risks of concern were identified for acute noncancer developmental toxicity.   No potential developmental toxicity and neurotoxicity risks were found for the hobbyist clear protective spray nonuser scenario.

N-methylpyrrolidone (NMP)

NMP is a widely used volatile organic compound produced/imported in quantities ranging from 100 to 500 million pounds per year.  Applications include petrochemical processing, engineering plastics, coatings, and agricultural chemicals.  The draft assessment was conducted for NMP used for paint stripping, which accounts for about 9 percent of the chemical’s total use, and focused specifically on exposure in small commercial facilities (fewer than 10 workers) and residential settings.  The EPA found that NMP is used in personal care products such as mascaras and nail polish, but did not assess this exposure.

Both inhalation and dermal penetration were assessed for NMP.  The available inhalation exposure data for workers and consumers are limited, which gave rise to a very wide range of potential exposures. Thus, the findings should be “viewed as uncertain,” says the Agency.  Since the only observed toxicological endpoint is developmental toxicity, the following findings are limited to women of child-bearing age:

• Workers may have potential risks of concern from dermal exposure when no gloves are worn.
• Consumers may have potential risks of concern from dermal exposure assuming appropriate gloves are not worn.
• Consumers may have potential risks of concern from inhalation exposure (although of lower concern than dermal exposure) if exposed for more than 4 hours at lower ventilation rates.

NMP is expected to have low persistence and low bioaccumulation potential in the environment.  Thus, potential risks to ecological organisms based on releases of NMP from paint stripping activities were not explored further in the assessment.  

Methylene chloride (dichloromethane, DCM)

DCM is a fast-acting, inexpensive, and popular solvent with many industrial and consumer applications.  U.S. demand for DCM is estimated at 181 million pounds per year.  There are only three DCM production facilities in the U.S.  Based on animal studies, the EPA views DCM as a probable human carcinogen.  U.S. OSHA has set a permissible exposure limit (PEL) and a short-term exposure limit (STEL) for DCM in the workplace.

The draft assessment focused on risks to workers in small facilities where DCM is used to strip paint.  The Agency extended its workplace data to risks to people using the chemical in residential environments.  In both cases, the Agency expressed concern about significant inhalation exposure during the use of DCM due to its high volatility.  The draft assessment did not address dermal exposure. 

EPA’s assessment found noncancer and cancer risks of potential concern for workers and noncancer risks for residential users of DCM-based paint strippers as well as for bystanders, particularly children.  Cancer risks varied between levels of a few in a million to a few in a thousand.  In five of the seven worker exposure scenarios, the cancer risk was estimated to be more than 1 in 1,000.  Workplaces in which immersion stripping of wood and wood and metal paint stripping are conducted posed the highest risks, according to the Agency, particularly in instances where OSHA’s limits were exceeded.  However, chronic potential risks of concern were identified for workers in almost all uses identified.

The assessment did not evaluate risks to the environment because DCM possesses moderate persistence, low bioaccumulation potential, and low hazard to aquatic organisms.

HHCB

HHCB is one of the most widely used polycyclic musk fragrance ingredients for a range of consumer products, including perfumes, cosmetics, shampoos, lotions, detergents, fabric softeners, and household cleaners.  The EPA reports that between 1996 and 2006, HHCB imports were between 1 million and 10 million pounds annually and have been on the rise since 2000; there is no U.S. production of the substance.  

Existing human health data, including a risk assessment performed by the EU, indicate negligible risks of concern.  The EPA also evaluated the weight of evidence from mutagenicity, subchronic, and endocrine studies and concluded that cancer data are not a critical data need.  Therefore, the human health risk was not assessed further.

An estimated 90 percent to 94 percent of the HHCB use volume is released to municipal wastewater.  HHCB is moderately bioaccumulative, and the Agency’s assessment looked mainly at risks resulting from direct exposure of aquatic species and underwater sediment-dwelling species.  Based on the available sampling data, the major risk is chronic effects to sediment-dwelling species in a small percentage of hotspots or areas highly contaminated with HHCB.  

Antimony and related compounds

Antimony and its compounds (mainly antimony trioxide, or ATO) are naturally occurring in the earth’s crust, mined, largely imported into the U.S. (87 percent), and used primarily as synergists in halogenated flame retardants applied to textiles and plastics.  Approximately 25 million pounds of ATO were consumed for this end use in 2011.  The toxics release inventory (TRI) for 2010 indicates that approximately 970,000 pounds of antimony compounds were released to land and roughly 15,700 pounds were released to water by industries that produce ATO-containing flame retardants.  On-site air releases were approximately 12,000 pounds, with about two-thirds from stacks.

According to EPA’s assessment, human exposure to ATO is estimated to be low, with food and water the primary sources.  The U.S. National Toxicology Program is currently engaged in a 2-year carcinogenicity study of ATO; the EPA states that it will review the results when they become available.  However, based on risk assessments completed in Canada and the EU, there is no evidence that this family of substances presents significant health risks to humans.

The risks to water-, sediment-, and soil-dwelling organisms were found to be significant only when concentrations of ATO exceed the hazard benchmarks identified for these organisms.  However, EPA’s review of environmental monitoring samples found only one exceedance of the benchmarks and no exceedances in the last 3 years.

Public comments on the draft assessments will be accepted by the EPA until March 11, 2013.  Nominations for peer reviewers of the drafts are also being accepted by the Agency.

Click here for the draft assessments.

William C. Schillaci
BSchillaci@blr.com