Information on contaminant concentrations in marine organisms is available from a number of marine monitoring programmes for sewage outfalls and dredging material disposal sites. The most recent available data set derives from the monitoring of the contaminated mud pits at East Sha Chau. Tissue samples are collected and analysis four times annually at both sites close to the disposal pits and at reference sites. The results of the biomonitoring have shown that there are no contaminants found to be at levels of concern, with the exception of Arsenic. Although mean concentrations for Arsenic were close to the Food Adulteration (Metallic Contamination) Regulations (Cap 132 sub. leg. V) Maximum Permitted Concentration in some species, the values were similar to those reported from elsewhere in Hong Kong. It appears from other analysis conducted under this programme that arsenic levels are elevated in sediments throughout Hong Kong in comparison to international levels of concern (ERM 1999c).

As is the case for marine sediments, data on organic contaminants is limited. This data gap was also addressed by the SUSDEV 21 baseline survey of marine toxics, which collected three species of marine organism at four survey stations during each of the four sampling cruises. Sampling stations included Mirs Bay, Port Shelter, Southwest Lamma and Deep Bay. Samples of fishes, crabs, prawns and shrimps (depending on species composition of the catch) were analysed for Total PCBs, Total PAH, Total DDT and TBT (ERM 2000c).

Among the marine biota analysed, the highest level of DDT was recorded in species of Gizzard Shag from Deep Bay (56.2 ug kg-1 wet weight), although these values were well within international action level guidelines for human health considerations. There was a clear trend in Total DDT concentrations increasing from east to west in the area of study, which is attributed to either elevated inputs of the pollutant from the Pearl River, or as a result of the documented phenomenon of increased accumulation by marine biota in waters of lower salinity such as estuaries. Total PCBs were commonly reported in the tissue samples above detection limits, with the highest concentrations from species in Deep Bay and Southern Waters (a Total PCB concentration of 25.0 ug kg-1 (wet weight) was recorded in Mantis Shrimp in southern waters off Lamma). However, all PCB levels were well within international levels of concern expressed as action levels for human health considerations. Although TBT and Total PAH levels were very low in biota, Naphthalene (a potentially carcinogenic PAH compound) was frequently reported at detectable concentrations.