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State of the Science Report for Biphenyl

Identity, Uses and Sources of Exposure

Biphenyl is a bicyclic aromatic with the chemical structure presented in Figure 1. It occurs naturally in coal tar, crude oil and natural gas (IPCS, 1999) and is also formed during the incomplete combustion of biomass, fossil fuels, rubber, plastic and municipal waste (NLM, 2002).

Results of a Section 71 survey (Environment Canada, 2001) indicate that the pattern of industrial use in Canada is similar to that reported elsewhere. Biphenyl is reported to be used internationally as a dye carrier and heat transfer fluid (Kroschwitz and Howe-Grant, 1991). Based on the results of the Section 71 survey, the total amount of biphenyl manufactured and/or imported into Canada for the year 2000 is greater than 100 000 kg (Environment Canada, 2001). However, the principal industrial source of biphenyl is its formation as a by-product of the hydrodealkylation of toluene to benzene.

Although biphenyl was previously used as a fungicide to control decay in citrus fruits (Nagy and Wardowski, 1981), biphenyl is no longer registered for such use in Canada (Masi, 2002). Biphenyl was also historically used as an intermediate in the production of polychlorinated biphenyls (PCBs) in the 1970s; however, due to the restricted and/or prohibited use of PCBs in many countries, this use is no longer prevalent (IPCS, 1999).

No consumer product uses were reported for biphenyl in the Section 71 survey (Environment Canada, 2001), and no data were identified on exposure to biphenyl through the use of consumer products; therefore, levels of biphenyl in consumer products are not expected to contribute significantly to exposure of the general Canadian population. Biphenyl has been measured in a cream containing coal tar used for treatment of cutaneous diseases, but this specific therapeutic use is not expected to result in widespread exposure of the general population.