Chlorinated hydrocarbons in sediments from Manila Bay,the Philippines

Polychlorobiphenyls (PCBs) and organochlorine pesticides were analysed in sediments collected during the summer monsoon period (rainy season) in order to assess the contamination of Manila Bay. Results were compared with previous determinations made during the winter monsoon period (dry season) in order to evaluate seasonal fluctuation of contaminant levels in the Bay. In both seasons, PCBs were present in concentrations higher than chlorinated pesticides. In the rainy season the median concentration of ΣPCB was 0.256 ng g^?1 dry weight (range 0.08–1.173 ng g^?1), followed by ΣDDT with 0.229 ng g^?1 dry weight (range 0.133–0.926 ng g^?1) and Σchlordane with 0.049 ng g^?1 dry weight (range 0.024–0.175 ng g^?1). Concentrations of chlorinated hydrocarbons in sediments were relatively low and, when concentrations determined in the rainy season and in the dry season were compared, in general, they did not show seasonal fluctuation with the exception of DDTs. Round the year, levels of these toxic, persistent and bioaccumulative contaminants in Manila Bay sediments were below threshold effect levels for marine biota.