Lindane is the gamma isomer of hexachlorocyclohexane and possesses the significant insecticidal activity. A number of studies (e.g. US EPA 1980, WHO 1991, CCME 1992) have reviewed the environmental fate and behaviour and aquatic toxicity of lindane to which the reader is referred for a more comprehensive assessment. An outline of the fate and behaviour, aquatic toxicity and bioaccumulative potential is presented below.

Direct and indirect application of lindane, agricultural run-off and industrial discharges are the principal sources of lindane in surface waters.

Data on concentrations of lindane reported in the marine environment are presented in Appendix D.

Lindane appears to be relatively stable in the water environment with some adsorption to sediment occurring (CCME 1992) . Abiotic degradation and volatilisation are not thought to be major removal processes. However, some biodegradation has been found to occur, with half-lives in the range of several days to a year reported in water and aquatic sediments

An exhaustive literature review on the toxicity of lindane to marine organisms has not been carried out for the purposes of this profile. The information provided in this section is taken from existing review documents (US EPA 1980, WHO 1991 and CCME 1992). The most sensitive groups of organisms have been identified.

Lindane can be considered to be highly toxic to both fish and aquatic invertebrates with acute effect concentrations generally occurring at concentrations > 1 µg l^-1. The EQS for all isomers of hexachlorocyclohexane, including lindane, is 0.02 µg l^-1 (annual average) in the water column. The standstill provision applies such that concentrations in sediments and/or shellfish and/or fish must not increase significantly with time.

Lindane has also been identified as an endocrine disrupting substance in in vivo assessments.

Lindane accumulates and persists in sediments and can pose a hazard to sediment dwelling organisms at concentrations above 0.32 µg kg^-1 according to Canadian interim marine sediment quality guidelines.

Lindane may be bioaccumulated in aquatic organisms (calculated log Kow of 3.72) and bioconcentration factors of 10² for aquatic invertebrates and fish have been reported. However, lindane appears to be rapidly eliminated once continuous exposure ceases and therefore biomagnification is not expected. For example, a half-life of less than 2 days was found for lindane depuration by bluegill sunfish (CCME 1992).

Potential effects include:

• toxic effects to invertebrates and fish at concentrations of all isomers of hexachlorocyclohexane, including lindane above the EQS of 0.02 µg l^-1 (annual average) in the water column;
• accumulation and persistence in sediments and can pose a hazard to sediment dwelling organisms at concentrations greater than 0.32 µg kg^-1 according to Canadian interim marine sediment quality guidelines;
• identification as an endocrine disrupting substance which may affect fish, birds or Annex II sea mammals.

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