The principal use of 4-chloro-3-methyl is as a general biocide to prevent micro-organisms degrading organic material. More than 50% of the production volume of 4-chloro-3-methyl phenol is used in metal working fluids. These fluids, used to lubricate and cool during metal grinding or in plant machinery, are rich in proteins which provide a source of nutrition for bacterial growth. The other major use is as a pharmaceutical preservative. For example, hand and body creams containing organic compounds in an aqueous phase may contain 4-chloro-3-methyl to prevent micro-organisms degrading the ingredients (Dixon et al 1997).

4-chloro-3-methyl phenol is authorised for use (according to Article 4 of Directive 91/414/EEC on the placing of plant protection products on the market, CEC (1991)) as fungicide in plant protection products in Ireland. However, its use as an agricultural fungicide has not been reported in the UK .

Other minor uses reported are as a disinfectant, in external germicides, as a preservative for cosmetics, medications, glues, gums, paints, inks, textile and leather goods. In medicine and veterinary medicine, use of 4-chloro-3-methyl phenol has been reported as a topical antiseptic (HSDB 1996).

Environmental release of 3-methyl-4-chloro phenol may occur from product formulation waste waters and by the use and disposal of products containing 4-chloro-3-methyl phenol, such as metal working fluids and pharmaceutical products.

Dixon et al (1997) provided data from the Environment Agency on concentrations of 4-chloro-3-methyl phenol in UK marine waters from the North-West.

The average for 1995 in marine and estuarine waters was 0.3 &micro;g l^-1 (a high of 0.6 &micro;g l^-1) (it should be noted that these annual average concentrations may be artificially low due to the treatment of <LOD results as zero, particularly when the LOD is high).

Monitoring data from the National Rivers Authority and the National Monitoring Programme Survey of the Quality of UK Coastal Waters are presented in Appendix D. However, 4-chloro-3-methyl phenol was not monitored in either survey.

Available monitoring data are very limited and can be considered insufficient for a comparison to be made with expected environmental concentrations and toxicity data or environmental standards.

In water, 4-chloro-3-methyl phenol will not hydrolyse to any significant degree. However, as the pH of the water becomes more alkaline, the phenolic group will dissociate increasingly. Photolysis is an important fate process for this compound in water, half-lives of 3.3 hours under a mercury vapour lamp to 46 hours under sunlight have been reported. Although biodegradation is not as important a fate mechanism in water as it is in soil, it is still significant with reported half-lives ranging from days to weeks. Sorption to suspended or bed sediments is likely to be limited (log Koc and Kow of 1.7 and 3.1 respectively) and high water solubility of the compound (4,000 mg l^-1 at 25^oC) (Dixon et al 1997).

An exhaustive literature review on the toxicity of 4-chloro-3-methyl 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 (Dixon et al 1997). The most sensitive groups of organisms have been identified.

Dixon et al (1997) were unable to find any reliable data on the toxicity of 4-chloro-3-methyl phenol to saltwater organisms. Until further data become available, it must be assumed they have broadly similar sensitivities as freshwater organisms.

In freshwaters, acute and chronic EC/LC50s of >=1 mg l^-1 have been reported for algae, crustacea and fish. No data could be located for sediment-dwelling organisms.

Dixon et al (1997) concluded that bioaccumulation was unlikely to occur.

Potential effects include:

• toxicity to algae, invertebrates and fish at concentrations above the EQS of 40 &micro;g l^-1 (annual average) and 200 &micro;g l^-1 (maximum allowable concentration) in the water column.

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