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- Bidleman, TF, et al.
(författare)
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Air-soil and air-water exchange of chiral pesticides
- 2003
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Ingår i: ENVIRONMENTAL FATE AND EFFECTS OF PESTICIDES Book Series: ACS SYMPOSIUM SERIES. - 0097-6156. ; 853, s. 196-225
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Tidskriftsartikel (refereegranskat)abstract
- The enantiomers of chiral pesticides are often metabolized at different rates in soil and water, leading to non-racemic residues. This paper reviews enantioselective metabolism of organochlorine pesticides (OCPs) in soil and water, and the use of enantiomers to follow transport and fate processes. Residues of chiral OCPs and their metabolites are frequently non-racemic in soil, although exceptions occur in which the OCPs are racemic. In soils where enantioselective degradation and/or metabolite formation has taken place, some OCPs usually show the same degradation preference; e.g. depletion of (+)trans-chlordane (TC) and (-)cis-chlordane (TC), and enrichment of the metabolite (+)heptachlor exo-epoxide (HEPX). The selectivity is ambivalent for other chemicals; preferential loss of either (+) or (-)o,p'-DDT and enrichment of either (+) or (-)oxychlordane (OXY) occurs in different soils.Non-racemic OCPs are found in air samples collected above soil which contains non-racemic residues. The enantiomer profiles of chlordanes in ambient air suggests that most chlordane in northern Alabama air comes from racemic sources (e.g. termiticide emissions), whereas a mixture of racemic and non-racemic (volatilization from soil) sources supplies chlordane to air in the Great Lakes region. Chlordanes and heptachlor exo-epoxide (HEPX) are also non-racemic in arctic air, probably the result of soil emissions from lower latitudes.The (+) enantiomer of alpha-hexachlorocyclohexane (alpha-HCH) is preferentially metabolized in the Arctic Ocean, arctic lakes and watersheds, the North American Great Lakes and the Baltic Sea. In some marine regions (Bering and Chukchi seas, parts of the North Sea) the preference is reversed and (-)alpha-HCH is depleted. Volatilization from seas and large lakes can be traced by the appearance of non-racemic alpha-HCH in the air boundary layer above the water. Estimates of microbial degradation rates for alpha-HCH in the eastern Arctic Ocean and an arctic lake have been made from the enantiomer fractions (EFs) and mass balance in the water column. Apparent pseudo first-order rate constants in the eastern Arctic Ocean are 0.12 y(-1) for (+)alpha-HCH 0.030 y(-1) for (-)alpha-HCH, and 0.037 y(-1) for achiral gamma-HCH. These rate constants are 3-10 times greater than those for basic hydrolysis in seawater. Microbial breakdown may compete with advective outflow for long-term removal of HCHs from the Arctic Ocean. Rate constants estimated for the arctic lake are about 3-8 times greater than those in the ocean.
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- Butt, CM, et al.
(författare)
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Spatial distribution of polybrominated diphenyl ethers in southern Ontario as measured in indoor and outdoor window organic films
- 2004
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Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 1520-5851 .- 0013-936X. ; 38:3, s. 724-731
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Tidskriftsartikel (refereegranskat)abstract
- Organic films were collected from indoor and outdoor window surfaces, along an urban-rural transect extending northward from Toronto, Ontario, Canada, and analyzed for 41 polybrominated diphenyl ether congeners (PBDE). For exterior films, urban SigmaPBDE concentrations were similar to10x greater than rural concentrations, indicating an urban-rural gradient and greater PBDE sources in urban areas. Urban films ranged from 2.5 to 14.5 ng/m(2) (mean = 9.0 ng/m(2)), excluding the regional "hotspot" Electronics Recycling Facility, compared to 1.1 and 0.56 ng/m(2) at the Suburban and Rural sites. Interior urban films (mean = 34.4 ng/m(2)) were 3 times greater than rural films (10.3 ng/m(2)) and were representative of variations in building characteristics. Indoor films were 1.5-20 times greater than outdoor films, consistent with indoor sources of HOES and enhanced degradation in outdoor films. Congener profiles were dominated by BDE-209 (51.1%), consistent with deca-BDE as the main source mixture, followed by congeners from the penta-BDE mixture (BDE-99:13.6% and -47:9.4%) and some octa-BDE (BDE-183:1.5%). Congener patterns suggest a degradative loss of lower brominated compounds in outdoor films versus indoor films. Gas-phase air concentrations were back-calculated from film concentrations using the film-air partition coefficient (K-FA). Mean calculated air concentrations were 4.8 pg/m(3) for outdoor and 42.1 pg/m(3) for indoor urban sites, indicating that urban indoor air is a source of PBDEs to urban outdoor air and the outdoor regional environment.
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- Schonnesson, LN, et al.
(författare)
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Three types of adherence to HIV antiretroviral therapy and their association with AIDS diagnosis, medication side-effects, beliefs about antiretroviral therapy, and beliefs about HIV disease
- 2007
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Ingår i: International journal of STD & AIDS. - : SAGE Publications. - 0956-4624 .- 1758-1052. ; 18:6, s. 369-373
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Tidskriftsartikel (refereegranskat)abstract
- One hundred and ninety-three adults with HIV taking antiretroviral therapy completed a questionnaire on demographics, health beliefs, medication side-effects, and adherence to dose, schedule, and dietary instructions. Three health beliefs indices were identified: antiretroviral therapy (ART) benefits, ART adherence self-efficacy, and beliefs about future HIV-related health concerns. Patients who experienced medication side-effects reported strong beliefs that HIV infection would cause them future health problems or distrust in the benefits of ART. AIDS diagnosis obtained through medical records or medication side-effects were not related to any of the three types of adherence. Beliefs about future HIV-related health concerns were associated with suboptimal dose adherence. Beliefs about ART benefits were associated with suboptimal schedule and dietary instructions adherence. Older age and partner were protective factors of schedule adherence. Data suggest that health beliefs may vary across type of adherence and that adherence behaviours may be a coping strategy to adjust antiretroviral therapy to one's daily living.
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