Most these products was tested into water, acetic

Most studies have concentrated on the potential for BPA exposure from dietary sources. In fact, a significant number of studies have been dedicated to determining BPA levels in foods, especially foods stored in cans with epoxy resin linings. A few other potential sources of BPA exposure, namely drinking water, air and dust, have received far less attention. While several studies have examined BPA leaching from landfills, additional studies are needed to examine these other potential sources and routes of exposure. (1)

Polycarbonate containers (e.g., Tupperware) intended to be used as reusable food containers, have the potential to leach BPA. Many of these containers are marketed for use in the microwave, although heating may increase BPA leaching levels. Nerin et al. examined the composition of a microwavable polycarbonate plastic container. BPA was found in the plastic at a concentration of 30 ?g/g plastic and the potential migration level was estimated at 6.5 ?g/g of food. However, this study only made leaching estimates, and its authors acknowledged that assessments of actual leakage from plastic products are still needed. In another study with potential implications for food safety, BPA levels in plastic stretch film used in food packaging were examined. An examination of five polyvinyl chloride stretch films indicated measurable BPA content in four samples that ranged from 43 to 483 mg/kg film. The migration of BPA from these products was tested into water, acetic acid and olive oil. Three of five films showed leaching into water and acetic acid, while four of five leached BPA into olive oil, illustrating the potential for BPA contamination of consumer food products. (1)

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Cigarette filters also contain relatively high levels of BPA and therefore may be a significant source of exposures in a human subpopulation. Cigarette components can be absorbed into the bloodstream via inhalation as well as absorption via the mucosal membranes in the mouth and respiratory tract; both of these routes would bypass the liver and thus the first-pass metabolism that occurs after ingestion of BPA. Several direct comparisons of smokers and non-smokers reveal higher levels of BPA metabolites in the urine of smokers, suggesting that this source of exposure cannot be discounted. Additional studies are needed to determine the amount of BPA that is absorbed into the body during the smoking of the filtered cigarette, but at this time, any assumptions about the rout of exposure form this source are not based upon experimental evidence. (2)

Metallic food cans are protected from rusting and corrosion by the application of epoxy resins as inner coatings. Many of these resins are synthesized by the condensation of BPA with epichlorhydrin to create bisphenol A diglycidyl ether. When incomplete polymerization occurs, residual BPA may leach from the epoxy resin and has the potential to contaminate stored foods. Several studies have documented conditions that support or enhance BPA migration from the coating of cans. These studies have obtained cans from manufacturers and performed carefully controlled studies on the influence of healing time, heating temperature, storage time, storage temperature, and other factors on the level of BPA migration. One of the earliest studies quantified BPA leaching at a range of 4-23 ?g of BPA per can. Kang et al. conducted a comprehensive study and found that heating temperature had a significant effect on BPA migration, to a greater extent than heating time. Vegetable oil and sodium chloride solutions were also found to significantly increase BPA leaching. Takao et al. also found an influence of temperature on the release of BPA from coated cans. While low levels of BPA were detected in water stored in unheated cans, when cans were heated to 100 Celsius, a normal temperature for the preservation of canned foods, the BPA concentrations in the water increased 1.7-55.4 times the unheated concertation. (1)

In studies of BPA migration from polycarbonate plastics conducted with the use of food-simulating liquids, BPA levels in ethanol and acetic acid differed with storage time and temperature but were higher than that in water. (3)

Most of the studies described below conclude with a statement about the low level of BPA leaching from a sing studied source. Very few studies have estimated total BPA exposure from multiple sources. (1)

Being one of the world’s highest production and consumption volume chemicals, widespread and continuous exposure through food and drinking water, BPA has become a public health concern. Although some regulatory authorities around the world questioned some of the low-dose animal studies, some evidence have shown the possible linkage between BPA exposure and observed human health effects. (4)

Data analysis

In all analyses, urinary BPA levels were log-transformed to normalize the distribution. Spearman correlations were calculated to compare the data on reported intakes of canned food, canned beverages, restaurant meals and exposure scores on the 24h food records.

Spearman correlations were also calculated to evaluate the correspondence between hypothesized sources of BPA exposure assessed by the 24h food records and observed urinary BPA levels. Multivariable linear regression models were used to evaluate the degree to which data collected on the urinary BPA levels. Primary exposures were evaluated as categorical variables and included canned foods, microwave meals, canned beverages and restaurant meals consumption. Exposure scores were additionally evaluated as continuous variables. Age, gender, education, BMI, income, occupation, and chronic health issues were evaluated as potential covariates. No individual variables were found to be associated with both urinary BPA levels and packaged food intake. Consequently only age and gender were included as covariates in the models. (5)