United States Environmental Protection Agency

About: United States Environmental Protection Agency is a government organization based out in Washington D.C., District of Columbia, United States. It is known for research contribution in the topics: Population & Environmental exposure. The organization has 13873 authors who have published 26902 publications receiving 1191729 citations. The organization is also known as: EPA & Environmental Protection Agency.

Phthalate-induced Leydig cell hyperplasia is associated with multiple endocrine disturbances.

Abstract: The possibility that exposures to environmental agents are associated with reproductive disorders in human populations has generated much public interest recently. Phthalate esters are used most commonly as plasticizers in the food and construction industry, and di-(2-ethylhexyl) phthalate (DEHP) is the most abundant phthalate in the environment. Daily human exposure to DEHP in the U.S. is significant, and occupational and clinical exposures from DEHP-plasticized medical devices, e.g., blood bags, hemodialysis tubing, and nasogastric feeding tubes, increase body burden levels. We investigated the effects of chronic exposures to low environmentally relevant DEHP levels on testicular function. Our data show that prolonged exposures to this agent induced high levels of the gonadotropin luteinizing hormone and increased the serum concentrations of sex hormones [testosterone and 17β-estradiol (E2)] by >50%. Increased proliferative activity in Leydig cells was evidenced by enhanced expression of cell cycle proteins, as determined by RT-PCR. The numbers of Leydig cells in the testis of DEHP-treated rats were 40–60% higher than in control rats, indicating induction of Leydig cell hyperplasia. DEHP-induced elevations in serum testosterone and E2 levels suggest the possibility of multiple crosstalks between androgen, estrogen, and steroid hormone receptors, whereas the presence of estrogen receptors in nonreproductive tissues, e.g., cardiovascular system and bones, implies that the increases in serum E2 levels have implications beyond reproduction, including systemic physiology. Analysis of the effects of phthalate exposures on gonadotropin and steroid hormone levels should form part of overall risk assessment in human populations.

Early Environmental Origins of Neurodegenerative Disease in Later Life

Abstract: Parkinson disease (PD) and Alzheimer disease (AD), the two most common neurodegenerative disorders in American adults, are of purely genetic origin in a minority of cases and appear in most instances to arise through interactions among genetic and environmental factors In this article we hypothesize that environmental exposures in early life may be of particular etiologic importance and review evidence for the early environmental origins of neurodegeneration For PD the first recognized environmental cause, MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine), was identified in epidemiologic studies of drug abusers Chemicals experimentally linked to PD include the insecticide rotenone and the herbicides paraquat and maneb; interaction has been observed between paraquat and maneb In epidemiologic studies, manganese has been linked to parkinsonism In dementia, lead is associated with increased risk in chronically exposed workers Exposures of children in early life to lead, polychlorinated biphenyls, and methylmercury have been followed by persistent decrements in intelligence that may presage dementia To discover new environmental causes of AD and PD, and to characterize relevant gene–environment interactions, we recommend that a large, prospective genetic and epidemiologic study be undertaken that will follow thousands of children from conception (or before) to old age Additional approaches to etiologic discovery include establishing incidence registries for AD and PD, conducting targeted investigations in high-risk populations, and improving testing of the potential neurologic toxicity of chemicals

Bird communities and habitat as ecological indicators of forest condition in regional monitoring.

Abstract: Ecological indicators for long-term monitoring programs are needed to detect and assess changing environmental conditions. We developed and tested community-level environmental indicators for monitor- ing forest bird populations and associated habitat. We surveyed 197 sampling plots in loblolly-shortleaf pine forests, spanning an area from Georgia to Virginia (U.S.A.) and representing a gradient in levels of anthropo- genic disturbance. Ninety of these plots were randomly selected from a sampling grid, permitting quantitative assessment of cumulative distribution functions for bird community and habitat parameters. Species were in- dependently classified into habitat assemblages indicating birds typical of disturbed habitat (e.g., shrubland, forest edge) and undisturbed habitat (mature forest). Relative abundances of these assemblages were used to form a bird community index—similar to the index of biotic integrity applied to aquatic systems—showing the effects of habitat disturbance on forest bird communities. Bird communities on the majority of the sample area (52-75%, 90% confidence interval) were dominated by disturbance-tolerant species. Sites dominated by mature-forest species were comparatively uncommon. Habitat assemblages appeared to be particularly useful tools for environmental monitoring; individual species abundance was positively correlated with assemblage species richness, and assemblage members showed consistent responses to variations in disturbance level. To a lesser extent, component species of nesting guilds showed this pattern of cohesive responses, but those of for- aging guilds did not. We also developed a habitat index based on habitat variables that predicted bird com- munity index values. Habitat and bird community indices were strongly correlated in an independent vali- dation dataset, suggesting that the habitat index can provide a reliable predictor of bird community status. The two indices may be used in combination, with the bird community index providing a direct measure of the status of the bird community and the habitat index providing a basis on which to separate changes in the bird community into local habitat effects versus other factors (e.g., landscape level effects, changes on winter- ing grounds).

Genotoxicity of industrial wastes and effluents

Abstract: In excess of several million pounds of genotoxic and/or carcinogenic industrial wastes are released into the U.S. environment each year. Chemical characterization of these waste materials can rarely provide an adequate assessment of their genotoxicity and potential hazard. Bioassays do not require prior information about chemical composition and can effectively assess the genotoxicity of complex waste materials. The most commonly used genotoxicity assay has been the Salmonella mutagenicity assay. Results with this system have shown that the genotoxic potency of industrial wastes can vary over 10 orders of magnitude, from virtually nondetectable to highly potent. Industries employing similar industrial processes generally release wastes of similar potency. Extremely high potency wastes include those from furazolidone and nitrofurfural production. Pulp and paper mills, steel foundries, and organic chemical manufacturing facilities also discharge wastes of noteworthy potency. Treatment and remediation of some wastes, such as pulp and paper mill effluents, have been shown to reduce or eliminate genotoxicity. However, in other cases, treatment and remediation have been shown to enhance genotoxicity, such as for fungal treatment of oils. Analyses of samples collected from areas known to receive industrial wastes and effluents have shown that genotoxins can accumulate in the receiving environment and have adverse effects on indigenous biota. The evaluation of hazardous wastes and effluents by genotoxicity assays may provide data useful not only for hazard identification but for comparative risk assessment.