Until the mid-1970s, biphenyl was used extensively in the manufacture of polychlorinated biphenyls (PCBs). The subsequent banning of PCBs meant that biphenyl's primary use was as a dye carrier in the textile industry. Barry and Wilkinson (1994) reviewed the data on biphenyl, but were unable to locate data on amounts used in the UK. However, in 1976 in the US, approximately 50% of the biphenyl manufactured was used as a dye carrier (Weaver 1979). The US EPA (1976) estimated that the market for biphenyl as a dye carrier would remain static or even increase by 1985. Other uses of biphenyl include:

• as a heat transfer agent, a market that was expected to remain static throughout the 1980s;
• as an impregnate in citrus fruit wrappers where it acts as a mild fungicide, a shrinking market given the increased efficiency of fruit transport; in the manufacture of plasticisers; and
• in optical brighteners (Weaver 1979).

Biphenyl is also a by-product of several important industrial processes, notably in: the manufacture of high octane motor and aviation fuels; catalytic cracking to form lighter gasoline components; and as a high boiling point component of coal tar, a component that is often used in the manufacture of creosote.

Little information is available on the volume of biphenyl produced annually. EC production was reported as >10,000 tonnes/year in 1985 (SRI 1985) and appeared to be confined to two manufacturers in Germany. No production was reported in the UK.

Biphenyl is a component of creosote, a substance that has widespread applications as a weather proofing agent for wood. Much of the biphenyl present in the creosote may, potentially, be leached to the aquatic environment or volatilised to the atmosphere. The other main threat to the aquatic environment is likely to be from by biphenyl being leached from landfills. For example, biphenyl may be present as a by-product in the wastewater produced during the manufacture of naphthalene feedstocks and hydrocarbon fuels.

Biphenyl's range of uses suggests that release to the aquatic environment from both point and diffuse sources will be of primary concern. However, few data exist to quantify biphenyl's presence therein.

Barry and Wilkinson (1994) found few data on the presence of biphenyl in the environment, partly because biphenyl is often present in complex organic matrices that are difficult to resolve and quantify.

The authors found no reported concentrations of biphenyl in the UK environment, although its presence in the River Thames was reported in a European Council document (CEC 1979).

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, biphenyl was not monitored in either survey.

At present, there is insufficient information to compare expected environmental concentrations with toxicity data or environmental standards.

The US EPA (1976) suggests that any biphenyl released to the aquatic environment will be rapidly removed (mainly by volatilisation). Mackay (1975) investigated the evaporation of low-solubility contaminants from water bodies to the atmosphere. The half-life of biphenyl in water 1 m deep was estimated to be 7.5 hours. It was reported that, for depths greater than 1 m, the half-life would be expected to increase. However, based on its low solubility (0.37x10^-1 g cm^-3) and log Kow of 3.9, it is probable that some adsorption to suspended solids or sediments will occur.

An exhaustive literature review on the toxicity of biphenyl 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 (Barry and Wilkinson 1994). The most sensitive groups of organisms have been identified.

Barry and Wilkinson (1994) reviewed data on the toxicity of biphenyl to saltwater organisms. Limited data were available, although the authors concluded that sensitivity was likely to be similar to that observed for freshwater organisms, with crustaceans and fish exhibiting greatest sensitivity.

Abernethy (1986) reported that the 24 hour LC₅₀ for Artemia sp. was 4 mg l^-1using nominal concentrations in a closed system. Donkin (1989) investigated the effect of biphenyl on the rate of feeding of the mussel Mytilus edulis obtained from an intertidal zone. The effect was expressed in terms of the biphenyl concentration in water and tissue required to reduce the feeding rate by 50%, the WEC50 and TEC50. The reported WEC50 and TEC50 were 0.30 mg l^-1 and 15.6 mg kg^-1 respectively.

Dill et al. (1982) reported a 96 hour LC50 for biphenyl on sheepshead minnow Cyprinodon variegatus of 4.6 mg l^-1 using nominal concentrations in open containers. No data could be located for sediment dwelling organisms.

Barry and Wilkinson (1994) found no data on the bioaccumulation of biphenyl in the marine environment.

However, they did report a study by Neff (1976) who investigated the accumulation and release of petroleum derived aromatic hydrocarbons by marine animals. An oyster Crassostrea virginica was shown to contain a concentration of 0.3 ppm of biphenyl in its tissue after being exposed to a fuel oil (1% oil in water) for 8 hours under flow through conditions. After removal of the oyster to uncontaminated seawater, the concentration of biphenyl in the tissue had fallen to 0.1 ppm after 5 days and to background amounts after 28 days. The experiment was repeated with a clam Rangia cuneta. After 8 hours exposure to the fuel oil contaminated seawater, the clam was observed to contain a concentration of 0.1 ppm of biphenyl in its tissue. This was removed in less than 3 hours in uncontaminated seawater suggesting that bioaccumulation is unlikely to be a problem.

The US EPA (1976) suggested that biphenyl was a hydrophobic substance and had a moderate tendency to accumulate in sediment and biota.

Potential effects include:

• toxicity of biphenyl to invertebrates and fish at concentrations above the EQS of 25 µg l^-1 (annual average) in the water column.

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