By Pat Rizzuto
The Agency for Toxic Substances and Disease Registry released on June 27 draft, updated toxicological profiles evaluating the health hazards posed by three chemicals and two related compounds found at some industrial facilities, superfund sites, and other hazardous waste sites.
The draft toxicological profiles discuss ways workers, the general population, military personnel, and special populations living or working around hazardous waste sites could be exposed to the substances.
The chemicals are:
• 1,1-dichloroethane (Chemical Abstracts Service No. 75-34-3), which is used to make other chemicals and to dissolve paint, varnish, and other coatings;
• 2,4-dinitrotoluene (CAS No. 121-14-2) and 2,6-dinitrotoluene (CAS No. 606-20-2), which are two of six dinitrotoluenes (DNTs) used in automobile air bags and to produce ammunition, explosives, dyes, and flexible polyurethane foams for beds and furniture;
• endosulfan, (CAS No. 115-29-7), an insecticide being phased out globally through means including the Stockholm Convention on Persistent Organic Pollutants (POPs Convention), which seeks to reduce or eliminate chemicals that persist in the environment, bioaccumulate in the food chain, are toxic, and can travel long distances from where they are produced or released; and
• hexachlorobenzene (CAS No. 118-74-1), a pesticide now banned in the United States and targeted for global elimination under the POPs Convention.
In a Federal Registernotice set for June 28 publication, ATSDR requested comments on the draft, updated profiles, and the submission of relevant additional studies, particularly unpublished studies, by Sept. 30.
Unlike the toxicological assessments the Environmental Protection Agency prepares for its Integrated Risk Information System, which are designed to provide information that risk managers and regulators need, ATSDR's toxicological profiles are designed for a wide-ranging audience with varied levels of technical expertise.
ATSDR's principal audiences are health professionals at the federal, state, and local levels; interested private sector organizations; and members of the public.
Each toxicological profile summarizes information, including results from toxicological and human studies, regulatory standards, recommended exposure limits, and voluntary standards such as workplace exposure limits approved by the American Conference of Governmental Industrial Hygienists.
In addition, where possible, ATSDR sets its own minimum risk levels (MRLs). These are not cleanup or action levels but rather are “intended only to serve as a screening tool to help public health professionals decide where to look more closely,” the agency said in each draft profile.
Depending on the information available to it, ATSDR's profiles can include acute MRLs, which are exposure levels that--if exceeded for one day to 14 days--may prompt public health professionals to examine a situation more closely; interim MRLs (15 days-364 days); and chronic MRLs (one year or longer).
ATSDR said data were insufficient to calculate inhalation or oral MRLs for 1,1-dichloroethane. “There is no reliable information on what levels of exposure to 1,1-dichloroethane have resulted in harmful health effects in people,” the draft profile said.
While scientists have observed birth defects in the offspring of exposed rats, the laboratory animals' exposure levels were high, 1,550 parts per million in air, ATSDR said.
To prevent adverse neurological and other health effects, the agency proposed three oral MRLs for 2,4-dinitrotoluene (2,4-DNT):
• an acute-duration MRL of 0.05 milligram per kilogram of bodyweight per day (mg/kg/day), which is the same as the agency set in its previous 2,4-DNT profile issued in December 1998;
• an intermediate-duration MRL of 0.007 mg/kg/day, which would be a slight increase over the MRL of 0.002 mg/kg/day set in 1998; and
• a chronic MRL of 0.001 mg/kg/day, which would be the first chronic MRL the agency would establish for 2,4-DNT.
To prevent adverse neurological and other health effects, the agency proposed two oral MRLs for 2,6-dinitrotoluene (2,6-DNT):
• an acute-duration MRL of 0.09 mg/kg/day, which would be the first acute MRL the agency would establish for 2,6-DNT; and
• an intermediate-duration MRL of 0.004 mg/kg/day, the same as the agency set for 2,6-DNT in 1998.
To prevent adverse neurological or immune effects of endosulfan, ATSDR proposed three oral MRLs:
• an acute-duration MRL of 0.007 mg/kg/day; the agency had not established an equivalent value MRL in its previous endosulfan profile released in September 2000;
• an intermediate-duration MRL of 0.005 mg/kg/day, the same as the agency set in September 2000; and
• the adoption of its intermediate-duration MRL of 0.005 mg/kg/day as the chronic-duration MRL.
ATSDR said it proposed to adopt the intermediate-duration MRL for the chronic-duration level because its calculations of a chronic level would have allowed a “slightly higher” exposures.
To be protective, therefore, it proposed to recommend that public health professionals use the 0.005 mg/kg/day oral MRL.
To prevent adverse neurological, reproductive effects, and liver effects, ATSDR proposed three oral MRLs for hexachlorobenzene:
• an acute-duration MRL of 0.008 mg/kg/day, the same as the agency set in its previous hexachlorobenzene profile issued in September 2002;
• an intermediate-duration MRL of 0.0001 mg/kg/day, the same as set in 2002; and
• a chronic-duration MRL of 0.00007 mg/kg/day, which would be slightly higher than the level of 0.00005 mg/kg/day the agency set in 2002.
Comments, due Sept. 30, should be marked Docket ID No. ATSDR-2013-0001 and submitted at http://www.regulations.gov.
MRLs that the agency set for these and other chemicals prior to the release of these draft toxicological profiles are available at http://www.atsdr.cdc.gov/mrls/mrllist.asp.
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