Environmental contaminants and the prevalence of hemic neoplasia (leukemia) in the common mussel (Mytilus edulis complex) from Puget sound, Washington, USA

The relationship between hemic neoplasia, a blood cell disorder in bivalve molluscs, and chemical contaminants was evaluated in the common mussel (Myt ilus edulis complex). Hemic neoplasia (HN) is endemic to mussel populations in Puget Sound. The prevalence of hemic neoplasia ranged from 0 to 30% in mussels from nine sites in Puget Sound, Washington. Organic chemical contam ination in sediment from these sites range from 0.1 to 64.0 ppm of polycycl ic aromatic hydrocarbons (PAHs) and 0.07 to 0.50 ppm chlorinated hydrocarbo ns. No relationship between the body burden of environmental contaminants a nd the prevalence of HN in mussels was identified. To evaluate the shortter m ability of chemical contaminants to induce HN in mussels, mussels, from a site where mussels were previously determined to be HN free, were fed micr oencapsulated PAHs (composed of a mixture of phenanthrene, flouranthene, an d benzo[a]pyrene) or PCBs (Aroclor 1254) and the prevalence of HN was asses sed after 30 days of exposure. Although an apparent in crease in HN prevale nce (20 to 30%) was observed in all treatments groups except the untreated controls, no significant difference in the prevalence of HN was observed be tween the control group of mussels fed corn oil (vehicle) and mussels fed e ither PAHs or PCBs in corn oil. A long-term (180-day) exposure study was co nducted to evaluate the influence of PAHs or PCBs in modulating the prevale nce of HN in a mussel population already exhibiting a moderate HN prevalenc e. Mussels, from a site where mussels were previously determined to exhibit a background prevalence of HN, fed microencapsulated PAHs, PCBs, and corn oil (vehicle) over a long time period (180 days), revealed an apparent incr eased prevalence of HN (30 to 40%) above the low levels (20%) initially pre sent. However, no significant difference in the prevalence of HN was observ ed between the control group of mussels fed corn oil (vehicle) and mussels fed either PAHs or PCBs in corn oil. Although chemical contaminants have be en proposed as a modulating factor in the development and promotion of HN i n bivalve molluscs from environmentally stressed and degraded habitats, we find no evidence that chemical contaminants induce or promote the developme nt of HN in the mussel M. edulis complex. (C) 1999 Academic Press.