Environmental Engineering Reference
In-Depth Information
Some dental composite materials (Kingman et al., 2012) are based on
bisphenol A-glycidyl methacrylate (bis-GMA) that may also contain
other monomer modifiers such as bisphenol A dimethacrylate
(bis-DMA) (Fung et al., 2000). BPA itself is not directly used in the
composite. It is the bis-DMA and bis-GMA (the prepolymer used can
have as much as 70% monomer) in the composite that can be converted
into BPA and leached into the saliva of patients (within 1-3 h after
dental sealant is applied) (Fleisch et al., 2010). The levels reported in
saliva are typically low; the highest reported is 931 µg/l.
4. Thermally printed receipts
Some leuco-dye-based thermal printing papers use BPA as a color
developer (Terasaki et al., 2007); these are used in point-of-sale
receipts, prescription labels, and some lottery tickets. Though the dye
paper comes into contact with individuals only for short durations, the
BPA load they deliver is 250-1000 times higher than that from plastic
bottles or from can lining. BPA from this source can be accidentally
ingested or transdermally acquired (Zalko et al., 2011) by handling the
paper. As might be expected, store cashiers were shown to have
relatively higher levels of BPA in their urine (Braun et al., 2011b).
Including thermal paper in recycling, streams can unexpectedly transfer
the BPA to other paper products such as toilet paper (Gehring et al.,
2004)!
With so many uses for the chemical, BPA is found ubiquitously in the
environment as well as in human body fluids and tissue (Murakami et al.,
2007; vom Saal and Hughes, 2005). Not surprisingly, 92.6% of adults in
the United States have BPA in their urine at a level averaging 2.4 µg/l in
females and 2.9 µg/l in males (Calafat et al., 2008). Lang et al.'s (2008)
studyhascorrelatedtheBPAconcentrationintheurineof1445adultswitha
range of their medical conditions (prevalence of diabetes, heart disease, and
liver toxicity). Particularly worrisome is the presence of BPA in follicular
fluid, amniotic fluid (Ikezuki et al., 2002), and cord blood (Schonfelder et
al., 2002), suggestive of fetal exposure.
Table 7.2
illustrates the body burdens of BPA from combined routes of
exposure, reported in recent years.
