Environmental Protection Agency Health Research Articles

A screening method for occupational reproductive health risk.

Most currently recognized occupational exposure limits do not consider reproductive toxicological end points consistently when establishing recommended exposure limits. In many cases the information is not available, but perhaps as often, existing data is not employed. Further, many manufacturer's material safety data sheets omit reproductive hazard information. A method for identifying potential reproductive toxins and screening levels for associated health risks useful for hazard communication and exposure control is presented. To date, the Registry of Toxic Effects of Chemical Substances lists between 5000 and 6000 chemicals, drugs, and natural substances that show a positive outcome in at least 1 reproductive effects study. This reproductive health risk assessment began with these substances. Using elements of the Environmental Protection Agency's health risk assessment process, the list was reduced to 213 chemicals during the hazard identification step. Occupational reproductive guidelines (ORGs) were developed in the dose-response evaluation step. At the time of this writing, 85% of the chemicals identified in the hazard identification step have had a screening level dose-response assessment completed. Of these, 13% are greater than or equal to a threshold limit value (TLV). The remaining 87% do not have a TLV or ORGs below the TLV. The reproductive toxins list, along with the corresponding dose-response-derived ORGs that have been completed, appears at the end of the text.

Herbicide Leaching under Tilled and No‐Tillage Fields

AbstractThe effect of no‐tillage practices on water quality exiting the root zone of deep, well‐drained fields is largely unknown. This project was initiated to determine herbicide leaching characteristics as influenced by tillage practice and herbicide formulation. The research site consisted of four adjacent (0.25‐ha) fields, two fields each dedicated to either tilled or no‐tillage management. One field in each tillage regime received a controlled‐release formulation of atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] and alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)‐acetamide, starch encapsulated], while the others received standard herbicide formulations of atrazine and alachlor. Both herbicide formulations were annually applied at the same rate: 1.7 kg ha−1 for atrazine and 2.8 kg ha−1 for alachlor. Atrazine, deethylatrazine [DEAT; 6‐chloro‐N‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], alachlor, and Br− concentrations were monitored with 12 suction lysimeters (six each at 1.5‐ and 1.8‐m depths) in each field. Alachlor was detected in <3% of all samples collected, regardless of tillage practice or berbicide formulation, while atrazine was detected in >41% of the samples. Under no‐tillage, atrazine was detected in <28% of the samples with <13% exceeding the U.S. Environmental Protection Agency Health Advisory level of 3 µg L−1 atrazine. Under tilled conditions, 53% of the samples contained atrazine, with 35% exceeding 3 µg L−1 atrazine. Averaged atrazine metabolite concentration of DEAT under no‐tillage was 0.52 µg L−1 vs. 0.39 µg L−1 for tilled fields. Similar Br− transport between tillage practices and reduced atrazine levels under no‐tillage fields suggest that no‐tillage management, on deep well‐drained soils, can have a positive impact on groundwater quality.

Disinfection By‐products

This discussion of disinfection by‐products, with an emphasis on toxicology, took place June 22, 1989, during the AWWA annual conference in Los Angeles, Calif. Michael J. McGuire, water quality director for the Metropolitan Water District of Southern California and manager of AWWA's Technical Advisory Workgroup on Disinfection Treatment and By‐products, interviewed Jennifer Orme, chief of the US Environmental Protection Agency Health Effects Assessment Section, and William H. Glaze, chairman of the environmental science and engineering department at the University of North Carolina, Chapel Hill.

Health Effects of Exposure to Diesel Engine Emissions: A Summary of Animal Studies Conducted by the U.S. Environmental Protection Agency's Health Effects Research Laboratories at Cincinnati, Ohio

In order to evaluate the potentially harmful effects of diesel engine emissions, inhalation exposure studies were carried out using a variety of animal species and strains, and measuring a wide range of toxicological parameters. Exhaust was provided by a 6 cylinder Nissan diesel engine operated 20 hours/day, 7 days/week, during a 2 month preliminary trial and 8 hours/day, 7 days/week during a 2 year, 4 month long-term study. The exhaust was diluted to produce a concentration of 6 mg/m3 particulate matter during the preliminary study and during the first year of the long term study and 12 mg/m3 thereafter. Exposure to diesel emissions did not result in detectable genotoxic effects as measured by increases in sister chromatid exchange (SCE), micronucleus testing and metaphase analysis in Chinese hamster and mouse bone marrow cells or in the morphology of cat sperm. SCE in lung cells from Syrian hamsters, however, was increased at the higher exposure level. The incidence of heritable mutations was not increased in mice. An increase in lung tumor incidence was detected in female Senear mice exposed from conception, but not in males, or in either male or female strain A mice exposed from 6 weeks of age. Voluntary activity was decreased in rats during exposure and learning ability was impaired in adult animals exposed during the early postnatal period. Susceptibility to an infectious challenge was increased in diesel exposed mice. Clearance of particles from the lung was found to be minimal even after 90 days recovery in clean air. Pulmonary function alterations in diesel exposed cats suggested the presence of a lesion restricting the air flow. The integrity of the lung as measured by leakage of 131I labeled protein into the alveoli did not seem to be impaired, but increased collagen synthesis suggested that fibrosis may develop with long-term exposure. The preliminary inhalation study resulted in the induction of xenobiotic metabolizing enzymes in the liver. In later studies, however, enzyme induction was found only in male mice injected with large doses of diesel particulate extract.