Population Effects

One widely reported incident was a large seabird wreck that occurred in the Irish Sea in the autumn of 1969 (Natural Environment Research Council Publication 

Some deaths of cormorants in the field in Holland were attributed to PCB poisoning on more substantial evidence than was available in the foregoing incident (Koeman 1972 Walker 1990a). Birds found dead had mean liver and brain levels of 319 and 190 ppm, respectively, which are not very different from those found in experimentally poisoned individuals. 

Organic Pollutants An Ecotoxicological Perspective, Second Edition 

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Mechanistic studies to identify how endocrine disrupting chemicals interact with hormone systems are required. Although population effects coupled with biomarkers of exposure are strongly suggestive of endocrine disruption, the effect could be secondary to metabolic toxicity. Establishing mechanisms may avoid the need to make decisions on a weight of evidence approach alone. 

Although eggshell thinning attributable to DDE exposure has occurred in birds in the UK, the lethal and siiblethal effects of the cyclodiene pesticides aldrin, dieldrin and heptachlor are also believed to have contributed to the population effects, particularly in the case of the sparrowhawk and peregrine falcon. Following the withdrawal of DDT and the cyclodienes from use in the UK, Europe and North America, bird of prey populations that were severely affected have shown partial or complete recovery. ... 

The relationship between biomarker responses and effects at the population level can be tested in both field experiments and more controlled experiments in mesocosms. It may be possible to define thresholds for biomarker assays performed on indicator species, above which population effects have been shown to occur. Indicator species may be either free living or deployed. The advantage of the latter is... 

Apart from the use of this approach to study the ecotoxicology of neurotoxic pollutants in the field, it also has potential for use during the course of environmental risk assessment. An understanding of the relationship between biomarker responses to neurotoxic compounds and effects at the population level can be gained from both field studies and the use of mesocosms and other model systems. From these it may be possible to define critical thresholds in biomarker responses of indicator species above which population effects begin to appear. In the longer term, this approach... 

While this qualifies as a small population-effect, the normal variability of individual susceptibility means that there may be a larger IQ deficit in particularly vulnerable individuals. 

Data of Fate of the Bioavailability l Short, long-term Population effects... 

In terrestrial ecosystems, atrazine effectively inhibits photosynthesis in target weeds and can also affect certain sensitive crop plants. Atrazine metabolites are not as phytotoxic as the parent compound. Degradation is usually rapid, although atrazine can persist in soils for more than one growing season. Soil fauna may be adversely affected shortly after initial atrazine application at recommended levels, but long-term population effects on this group are considered negligible. 

Deaths of nontarget species of birds after eating 1080-poisoned baits have been reported (Spurr 1979 Mcllroy 1984 Fry et al. 1986 Hegdal et al. 1986 Mcllroy et al. 1986a), although population effects have not yet been demonstrated. Birds of several species were found dead after 1080 baits were applied to kill California ground squirrels (Spermophilus beecheyi), but only Brewer s blackbird... 

Wheat 1 app of 5 g a.i./ha or 1 app of 5 g a.i./ha followed by 2nd app of 7.5 g a.i./ha Conclusions only possible for Microhymenoptera and lacewings, with moderate population effects reported for lacewings Effects on Lacewings were reversible but full recovery not reported during study... 

Lipton RB. Assessment of cognitive function of the elderly population effects of darifenacin. J Urol 2005 i73 493. 

Very suitable for Box B applications are mechanism-specific in vitro bioassays which have been linked to long term in vivo toxic effects (Murk et al., 1996 Foekema et al., 2008) and even to chronic population effects when the relationship with long term health effects have been... 

Bioindicators of effect in the field such as intersex index (ISI) and population decline in gastropods are useful to reveal causal relationships between the exposure to toxic compounds and population effects on local marine organisms. When these effects correspond to the effects predicted based on bioassays in the laboratory, for example expressed as PAF of species, these field effects in gastropods, can be used as a bioindicator for the local ecotoxicological health status. 

Heaney, R. P. (2003). Normalizing calcium intake Projected population effects for body weight. J. Nutr. 133, 268S-270S. 

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