PLASTICS AND HEALTH IMPACTS - Plastics and Environmental Sustainability - page 362

levels that far exceed those resulting from migration via packaging!
Examples include cinnamon (524 ppm) (Lafeuille et al., 2009), some
cheeses (up to 5000 ppb) (Tang et al., 2000), or raw avocado. Also,
cigarettes contain up to 147 µg styrene/cigarette (Cohen et al., 2002), and
smoking is a major route of personal exposure to styrene.
However, an expert panel of scientists convened by the National Toxicology
Program (NTP) recently recommended that styrene be listed in the 12th
Report as being “reasonably anticipated to be a human carcinogen”
(National Toxicology Program, 2008). Their process relied on a review of
published studies in arriving at this classification. 7 There is evidence from
occupational exposures (Budroni et al., 2010; Cocco et al., 2010; Huff and
Infante, 2011; Infante and Huff, 2011) and animal studies (Huff, 1984)
to support the potential carcinogenicity of the monomer. Also, styrene
7,8-oxide, the primary oxidation product of the monomer, is mutagenic
(Filser et al., 1993). Occupational exposure to styrene increases the risk of
lymphatic and hematopoietic carcinoma. Studies on occupational exposure
did show increased cancer risk due to exposure (Delzell et al., 2006; Kolstad
et al., 2012). In contrast, a 2013 study (Collins et al., 2013) on 16,000
cases of occupational exposure to styrene found no credible correlation
between exposure and cancer. While the evidence is not always consistent,
there appears to be enough credible data to seriously pose the question
of carcinogenicity of styrene and related compounds. Despite the level of
uncertainty in the reported data, the precautionary stance adopted by the
NTP is warranted and styrene does deserve closer attention at least until the
issue of carcinogenicity is resolved.
8.3.1 Exposure to Styrene from Packaging
The adverse impacts of human exposure depend on the total daily intake
(TDI). Styrene exposure in US populations was estimated to be less than
0.3 (mcg/kg body weight/day) in nonsmokers and <3.51 and <2.86 (mcg/
kg body weight/day) in smokers ages 12-19 years and 20-70 years,
respectively (NTP, 2006). Tang et al. (2000) arrived at TDI values of
18.2-55.2 µg/person/day (6.7-20.2 mg/person/year) of styrene. However,
most (~98%) of this intake was attributed to inhalation rather than to
ingestion with food (amounting to only 0.2-1.2 µg/kg bw/day). But a
Canadian study (Newhook and Caldwell, 1993), by contrast, found food to
be the leading source of styrene (0.11 µg/kg bw/day) making up the TDI. An