IARC MONOGRAPHS ON THE EVALUATION OF CARCINOGENIC ...

200 μg/kg, although 77% of the foods had levels below 10 μg/kg and 26% had levels
below 1 μg/kg (Gilbert & Startin, 1983).
Similar surveys were carried out by the Food Safety Directorate in 1992 and 1994 in
the United Kingdom, with styrene concentrations similar to those found in the 1983
survey. Within each food type, higher levels of styrene were generally found for products
with high fat content or packed in small containers (Ministry of Agriculture, Fisheries
and Food, 1994).
Between 1991 and 1999, the Food and Drug Administration’s Total Diet Study in the
USA analysed 320 different foods and found styrene residues in 49 of them. In 258
samples containing styrene, the mean concentrations for individual food items varied
between 10 μg/kg (eggs) and 274 μg/kg (strawberries). The median concentration for the
49 foods was 21 μg/kg (Food and Drug Administration, 2000).
Several assessments have been made of estimated daily intake (EDI) of styrene in
food packaged in polymers or copolymers of styrene. In 1981, the Food and Drug Administration
in the USA measured the migration of styrene over a 24-h period from foam,
impact and crystal polystyrene cups into 8% ethanol and water at 49 °C. The observed
migration was 0.036, 0.064 and 0.210 μg/cm 2 , respectively. This corresponds to 6 μg
styrene from a 2 dL (8 oz.) foam cup. Migration from foam cups into hot water, tea and
coffee was one fifth of these levels: approximately 1 μg from a 2 dL (8 oz.) cup (Varner
& Breder, 1981). In a 1983 study, the EDI of styrene monomer from polystyrene food
packaging, including polystyrene foam cups, was in the range of 1 to 4 μg per day
(Ministry of Agriculture, Fisheries and Food, 1989). More recently, Lickly et al. (1995)
estimated total dietary intake of styrene monomer from polystyrene food-contact
polymers to be 9 μg per day.
Styrene has been detected at low levels (ppb) in several foods and beverages which
had not previously been in contact with styrene-containing packaging materials (Maarse,
1992a,b; Steele, 1992, Steele et al., 1994). Much higher levels (around 40 mg/kg) have
been measured in cinnamon, and enzymatic degradation of cinnamic acid derivatives
was proposed as a possible source (Oliviero, 1906; Ducruet, 1984). The low-level occurrence
of styrene in other foods has been suggested to result from enzymatic and/or
microbial activity, but it is unclear to what extent these processes are, in fact, responsible
for the levels detected (Steele et al., 1994; Tang et al., 2000).
1.5 Regulations and guidelines
1.5.1 Exposure limits and guidelines
STYRENE 459
Occupational exposure limits and guidelines for styrene are presented in Table 8. A
tolerable daily intake (TDI) of 7.7 μg/kg bw for styrene has been established by WHO
(1993), with a guideline value of 20 μg/L in drinking-water. The Environmental
Protection Agency (2001b) has set a maximum contaminant level (MCL) for styrene in
public water systems in the USA at 0.1 mg/L.