Environmental Engineering Reference
In-Depth Information
Figure 7.2
Examples of non-monotonic dose-response curves. Above:
Effect of tumor volume in mice on the BPA levels in drinking water shows
an inverted-U response. Numbers on the horizontal axis refer to µg BPA/l
of drinking water available to the mice. These correspond to 0-500 pg of
BPA/kg body weight. Below: Suppression of adiponectin release from
human breast adipose explants by BPA and estradiol (E
2
). (Hugo et al.,
2008).
Source: Jenkins et al. (2011).
7.2.4 Safe Levels of BPA
The official “safe dose” used by the FDA for BPA is the USEPA reference
dose of 50 µg/kg body weight/day, based on a high-dose study on a
generation of adult mice and rats (Vogel, 2009). As was the practice in the
1980s, the lowest dose at which adverse effects were observable, multiplied
by safety factor of 10
3
, was used to arrive at the “safe” level. Numerous later
studies (Akingbemi et al., 2004; Al-Hiyasat et al., 2002; Bindhumol et al.,
2003; vom Saal et al., 1998), however, show adverse responses well below
this “safe” dose of 50 µg/kg body weight/day. In 2007, an expert panel of
38 scientists convened by the NIEHS, meeting in Chapel Hill, NC, reviewed
the available data and arrived at the consensus view that the current levels
of BPA in humans exceed those that result in adverse health impacts in
animals (Expert Panel on BPA, 2007). Over 100 peer-reviewed studies show
adverse effects in animal models (vom Saal and Hughes, 2005) at levels
that are sometimes orders of magnitude lower than the reference dose. In
mice, for instance, ingestion of only 2 ng/g body weight of BPA resulted in
changes in the preputial glands and epididymis (vom Saal et al., 1998): this
dosage was estimated to be lower than that ingested in the first hour after
application of a dental sealant! The National Toxicology Program (NTP) in
2008 also expressed concerns on low-dose effects of BPA.
for use with no further testing. The growing body of data, however, has
helped change the regulatory environment; in 2010, the FDA slightly
changed its position on BPA agreeing with the NTP view while still
maintaining BPA to be a safe chemical at the levels found in food. The use
of PC in baby bottles (and baby cups) has since been banned in Canada
in 2010, in the European Union, in China in 2011: the US FDA adopted a
