Reduced growth of the aquatic angiosperm Spirodela oligorhiza was reported following exposure to 5 mg/l PCBs (Aroclor 1242) for 14 days (Mahanty 1975). Symptoms of toxicity included reduced frond size with a characteristic striped chlorosis.
The toxicity of PCBs to freshwater invertebrates is variable, even between closely related species. Toxicity is related to the degree of chlorination, although this is not a direct correlation, as the most toxic congers are often those in the mid-range of chlorination (WHO 1993). Acute LC50 values range from 0.01 to 0.61 mg/l (Mayer and Ellersieck 1986).
The toxicity of PCBs to freshwater fish also varies between species and PCB mixtures. Test conditions, such as the temperature and hardness of the water do not strongly influence toxicity. Acute LC50 values range from 0.008 to 60.9 (Kimura et al. 1974; Nebeker et al. 1974; Passino and Kramer 1980; Mayer and Ellersieck 1986).
The use of PCBs has been progressively restricted in the UK since the 1970s, and in 1986 their sale and use in new plant and equipment was banned. Many PCBs are highly resistant to degradation or metabolism, they are readily bioaccumulated, and they continue to persist in the environment, several decades after their use was initially restricted. Although levels are lower compared to the 1960s, PCBs are still released to the atmosphere through cycling from environmental processes (Meijer et al. 2002). PCBs have recently been identified in air sampled from hazardous waste sites (WHO 1993; Ruokojarvi et al. 1995; Eisler 1996; ATSDR 2000).
|Critical Load/ Level|
No estimate available