Potential Carcinogenicity of Butyl Benzyl Phthalate
This chapter discusses the available carcinogenicity data on BBP and the possible mechanisms for its potential carcinogenesis. It explores the implications of early-life exposure and assessment of potential breast cancer risk. 12.1.1 ProductionBBP is synthesized by the reaction of the monobutyl ester of phthalic acid with benzyl chloride . It has a high production volume in the U.S., which increased from 1 million pounds reported in 1990  to 50-100 million pounds in 2002 . 12.1.2 Use and OccurrenceBBP is a solvent, additive, and general plasticizer used in a number of industrial and household products. More than 70% is used as a plasticizer, mainly in vinyl floor tiles, foam, carpet backing, and cellulosic resins [4, 5]. Other plasticizer uses of BBP include coatings for leather and textiles, calendaring of films, and packaging of medical products and in printing inks, adhesives, sealants, and paints. Nonplasticizer uses of BBP include uses as pesticide carriers and uses in cosmetics, fragrances, munitions, industrial oils, and insect repellants [5, 6]. Due to the concern for endocrine-disrupting effects of phthalates, the manufacture, sale, and distribution in commerce of toys and child care articles that contain BBP and certain other phthalates at concentrations exceeding 0.1% in the state of California have been illegal since January 1, 2009. The US Consumer Product Safety Improvement Act of 2008 prohibits the sale in the United States of any “children’s toy or child care article” individually containing concentrations of more than 0.1% BBP as of February 10, 2009. Throughout the stages of production, distribution, and disposal, BBP can be released into air (indoor and outdoor), water, and soil . According to the California Toxic Release Inventory Program, 9 tons of BBP was emitted into the air in California in 2006 . Measurements of BBP in outdoor air taken 100 m from a poly(vinyl chloride) (PVC) flooring factory have been reported to be as high as 0.40 µg/m3 .In the U.S., BBP has been detected in surface waters
at levels ranging from 0.2 to 4 µg/L . BBP has also been detected in raw and treated drinking water , marine sediments, soil, and biota such as some fish and invertebrates [3, 7, 10]. Foods detected with BBP include milk (mean concentration 1.2 ng/g) , spices, eggs, and breakfast cereals, with levels up to 0.5 mg/kg . Sources of BBP in foods include migration into the foods from its use as a plasticizer in food-packaging materials. BBP can also be a contaminant of indoor dust. For example, Guo and Kannan (2011) measured the levels of BBP in indoor dust from Albany, New York, and compared them to samples from six Chinese cities . The median level (dry weights) of BBP in the dust samples from New York was 21.1 µg/g compared to 0.1-0.6 µg/g from the Chinese cities. 12.1.3 Exposure and BiomonitoringOccupational exposure to BBP may occur during the production of BBP, the processing of BBP-containing PVC, including coatings and films, and the use of intermediate and end products . For the general population, exposure to BBP and its metabolites can come from consumer products such as food and food packaging, cosmetics such as nail polish, fragrances, medical devices, baby products, and children’s toys , as well as from indoor dust . On the basis of product data and the total daily BBP intake calculated from urinary levels of monobenzyl phthalate (MBzP), the principal BBP metabolite in humans, estimates were made of the contributions from different exposure routes to the total daily intake . Dietary intake was estimated to be the major source of BBP exposure in the US population in all age groups, accounting for over 58% of exposure from all routes. Dermal absorption of BBP-containing dust was estimated to be another important route of exposure in infants and toddlers (approximately 40% contribution). Several biomonitoring studies conducted in the United States have assessed exposure to BBP in the general population as well as in specific populations, such as infants, pregnant women, and firefighters (Table 12.1) [13-15]. Urinary levels of the BBP metabolite MBzP have been used as a biomarker of exposure for BBP in biomonitoring.