Persistent organochlorines in beluga whales (Delphinapterus leucas) from the St Lawrence River estuary--I. Concentrations and patterns of specific PCBs, chlorinated pesticides and polychlorinated dibenzo-p-dioxins and dibenzofurans

Blubber samples from beluga whales (Delphinapterus leucas) in the St Lawrence River estuary were analysed for PCB congeners (ortho- and non-ortho-substituted) and other persistent organochlorines as well as chlorinated dibenzo-dioxins/furans (PCDD/Fs). Major individual components (mean concentrations > 1 microg g(-1)) were 4,4'-DDE, -DDD and -DDT, T12 (a toxaphene-related compound), trans-nonachlor, oxychlordane, mirex, HCB, tris(p-chlorophenyl) methane and dieldrin. Concentrations of SigmaPCBs (8.3-412 microg g(-1)), SigmaDDT (3.36-389 microg g(-1)) and mirex (0.18-6.8 microg g(-1)) were particularly elevated relative to other odontocetes in Canadian waters. SigmaDDT, PCBs (as Aroclor), mirex and T12 concentrations were positively correlated with age of adult females (> 10 years) but only weakly, or not significantly, correlated with age of adult males. PCDD/Fs were present at low ng kg(-1) levels and consisted mainly of penta- and hexachlorofurans, and hepta- and octachlorodioxin. CB126 (3,3',4,4',5-PCB) was the most prominent non-ortho-substituted PCB congener in beluga blubber. Total TCDD toxic equivalents averaged 330 ng kg(-1) in females and 1400 ng kg(-1) in males and were dominated by CB126, and the mono-ortho-substituted congeners CB105 and CB118. Biomagnification factors (BMFs) for mirex and SigmaPCB from fish to beluga ranged from 11 to 16, and were similar to BMFs in Arctic animals, indicating that elevated levels in St Lawrence animals are a consequence of relatively high levels of recalcitrant organochlorines in prey of the beluga in the St Lawrence river system.     

Effects of the phenylurea herbicide isoproturon on periphytic diatom communities in freshwater indoor microcosms

The toxic effects of the phenylurea herbicide Isoproturon -IPU: (3-(4-isopropylphenyl)-1, 1-dimethylurea)-were studied on the colonization of periphytic diatom communities, within indoor microcosms consisting of a mixed biotope (water column and natural sediment) and two biological species-rooted macrophyte cuttings (Elodea densa) and benthic bivalve molluscs (Corbicula fluminea). The periphyton, essentially composed of diatoms, was collected on artificial substrata (glass slides) in the upper layers of the water column, after two periods of exposure (34 and 71 days). IPU was initially added in the water or in the sediment compartment, at two nominal concentrations (L1 and L2 levels) for each contamination source-5 and 20 microg litre(-1) and 100 and 400 microg kg(-1) in sediment (w/w) respectively. The effects of IPU on the density and community structure of periphytic diatoms are described. A marked reduction in the diatom density was observed after 34 days exposure to the lower concentration of IPU in the water (5 microg litre(-1)). For the L2 levels, the very small number of live cells present did not permit quantification of the diatom density. After 71 days, recovery in community parameters occurred for the two contamination levels of the sediment and water column sources. Samples collected in the experimental units contaminated with the L2 levels were dominated by heterotrophic and smaller diatom species, such as Sellaphora seminulum. Data treatment based on factorial discriminant analysis enabled us to distinguish the different contamination conditions, with only 11 species from the 130 taxa identified.     

Effects of ethylenediurea (EDU) on ozone-induced acceleration of foliar senescence in potato (Solanum tuberosum L.)

Experiments were conducted to examine the effects of the anti-ozonant ethylenediurea (EDU) and chronic ozone (O3) exposure on leaf physiology and senescence in an O3-sensitive potato cultivar (Solanum tuberosum L. cv. Norland). A dose-response experiment showed that an EDU concentration of 15 mg l(-1) soil (given as a soil drench) provided complete protection from accelerated foliar senescence induced by exposure to 0.1 microl l(-1) O3 for 5 h day(-1) for 11 days. EDU doses of 45 and 75 mg active ingredient l(-1) soil also gave protection but were associated with symptoms of toxicity and delayed senescence. In further experiments, plants were given 0 or 15 mg EDU l(-1) soil and exposed to clean air or 0.1 microl l(-1) O3 for 5 h day(-1) for 14 days. Chronic O3 exposure in the absence of EDU resulted in accelerated foliar senescence, characterized by early declines in net photosynthesis and Rubisco quantity in O3-treated plants relative to controls. EDU in the presence of O3 gave complete protection against symptoms of accelerated senescence. Senescence was not delayed in plants that received EDU in the absence of O3, and no symptoms of EDU toxicity were evident. The results suggest that EDU-induced tolerance to O3 was not based on 'anti-senescent' properties of this anti-ozonant.     

Effect of ozone on net photosynthesis in oat (Avena sativa) and duckweed (Lemna gibba)

Short exposure to ozone depressed photosynthesis in both oat and duckweed at concentrations above 140 microg m(-3) and 300 microg m(-3), respectively. The effect on exposed oat flag leaves was age-dependent, with maximum susceptibility to ozone 10-20 days after emergence of the panicle. In duckweed, photosynthesis was more sensitive to differences in ozone concentration than to differences in duration of exposure.     

Response of thermal stressed bobwhite to organophosphorus exposure

Constant and intermittent cold stressed juvenile northern bobwhite (Colinus virginianus) were exposed to chlorpyrifos, an organophosphorus insecticide, following avian dietary LC(50) test procedures. Chlorpyrifos concentrations ranged from 100 to 1000 ppm; ambient temperatures (T(a)) included 35.0 (control), 32.5, 30.0 and 27.5 degrees C. Survival decreased significantly under constant cold conditions. Non-survivors averaged 33% weight loss, but survivor weight dropped with increasing dose and decreasing T(a). Control quail at all temperatures maintained a constant body temperature (T(b)); however, T(b) of dosed quail fell with increasing dose and decreasing T(a). Non-surviving cold stressed quail had higher cholinesterase (ChE) activity that non-survivors at 35 degrees C; in addition, dead quail failed to average the 50% inhibition of ChE used to implicate a ChE depressant in death. Daily exposure of quail to 12 h of warmth increased survival. Survivors of intermittent cold stress experienced less weight loss than constant cold survivors due to reduced metabolic costs. Synergistic effects were evident in juvenile northern bobwhite exposed simultaneously to chlorpyrifos and cold stress; however, mortality and certain sublethal effects were mitigated when cold exposure was intermittent.     

Multi-criteria analysis and risk assessment

ELECTRE or Concordance Analysis is a French system of multicriteria analysis which is used in economics.The application of ELECTRE for hazard evaluation and risk assessment of chemical substances is suggested, and a first attempt in adapting it for this purpose is presented.     

Induction of aryl hydrocarbon hydroxylase by chlorinated dibenzofurans in rats

Five of 25 chlorinated dibenzofurans induced aryl hydrocarbon hydroxylase in rats when administered orally at 40 μg/kg body weight. Active inducers included the three congeners with chlorines in all four lateral positions and the 2,7- and 2,8-dichlorodibenzofurans. The findings agree well with other studies involving common congeners, but do not agree with findings in that congeners with three lateral chlorines were inactive .