Birds, developmental effects

Metal uptake has been linked to developmental effects in several bird studies 71, 97, 100). Brain lesions have been documented in lead exposed chick embryos 101). One study revealed that nestling deformities in pied flycatchers were linked to metal exposure while great tits inhabiting the same metal contaminated site did not show nestling deformaties 70). Slow growth rates from heavy metal exposure have also been demonstrated in natural populations 70, 80). Nestling survival rates of several bird species exposed to metals have been examined in the lab and field 66, 70, 102) yielding different results for different metals. 

Although chemicals are now used extensively in the control of rice pests, the demand for chemicals in this field is expected to be much greater in the future. Many chemicals now available have not been tested in countries where severe losses occur. In the developmental field, more satisfactory herbicides are needed for the control of broad-leaf weeds and grasses, better fungicides are needed to supplement breeding work for the control of foliar rice diseases more effective seed-treatment chemicals are needed for rice sown in water and satisfactory chemical repellants are needed to prevent losses from bird pests on maturing rice. 

Although drugs such as acetaminophen bind to AhR, the majority of AhR agonists or antagonists are environmental chemicals. Polychlorinated diben-zodioxins such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), dibenzofu-rans, biphenyls, and a number of other chemicals are widespread pollutants in aquatic ecosystems. These compounds cause a high reproductive and developmental toxicity, which is mediated via binding to the AhR. Thus they pose a serious threat to many populations of mammals, birds, and fish. Various adverse effects—including structural malformations, reduced fertility, tumor promotion, immunotoxicity, and skin disorders like chloracne—have been observed [139]. 

The investigation of the behavioural effects of lead in animals has drawn on all aspects of experimental psychology. Only studies employing rats or mice will be discussed here, although a large body of evidence is available for other animals (including fish, birds, sheep and primates). The behavioural effects of developmental lead exposure are summarized in Table 7. The doses and routes of administration for the studies outlined here are shown in Table 7. 

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