|
(21-06) Risk to Breeding Success of Ardeids in Hong Kong due to Persistent Organic Contaminants in Eggs . Connell, Des*,1,3, Lam, Paul1, Minh, T2, Tanabe, S2, Wong, Bryan1, Lam, Michael1, Wong, L1, Wu, Rudolf1, Richardson, Bruce1, 1 Centre for Coastal Pollution and Conservation, Department of Biology and Chemistry, City University of Hong Kong, Hong Kong, Peoples Republic of China3 School of Public Health, Griffith University, Meadowbrook, Qld., Australia2 Centre for Marine Environmental Studies, Ehime University, Tarume 3-5-7 Matsuyama 790-8566, Japan ABSTRACT- Eggs of the Ardeid species, the Little Egret ( Egretta garzetta) and the Black-faced Night Heron ( Nycticorax nycticorax) were collected from two egreteries located in the New Territories of Hong Kong with one located near the internationally acclaimed wetland reserve, the Mai Po Marshes, the other in a remote site ( A Chau). The eggs were analsed for organochlorine compounds including the DDTs, PCBs, hexachlorocyclohexane ( the HCHs) and the chlordanes. All of the organochlorine compounds under investigation were detected in the eggs of both species with significantly higher concentrations in the Little Egret than the Night Heron. The DDTs consisted of mainly of DDE with levels ranging from 85 to 95% of the total. All of the organochlorines had linear concentration probability distributions on a log-normal basis which were used to evaluate exposure associated with these compounds as part of a probabilistic risk assessment. A linear dose response relationship for the percentage reduction in the survival of young associated with DDE in eggs was developed. This probabilistic relationship was used to establish the threshold ( 1000 ng/g wet weight) at which there was a significant reduction in the survival of young above zero. This threshold and the exposure relationships were used to calculate the Risk Quotient (RQ) which had a 12.4 and 40.9% probability of exceeding unity for the Night Herons and Little Egrets respectively. These results suggest that the DDTs in eggs would be likely to be associated with adverse effects on the survival of young, particularly the Little Egret. Key words: breeding , birds, DDT, probabalistic risk assessment |
