Components of plastic: experimental studies in animals and relevance for human health

Abstract

Components used in plastics, such as phthalates, bisphenol A (BPA), polybrominated diphenyl ethers (PBDE) and tetrabromobisphenol A (TBBPA), are detected in humans. In addition to their utility in plastics, an inadvertent characteristic of these chemicals is the ability to alter the endocrine system. Phthalates function as anti-androgens while the main action attributed to BPA is oestrogen-like activity. PBDE and TBBPA have been shown to disrupt thyroid hormone homeostasis while PBDEs also exhibit anti-androgen action. Experimental investigations in animals indicate a wide variety of effects associated with exposure to these compounds, causing concern regarding potential risk to human health. For example, the spectrum of effects following perinatal exposure of male rats to phthalates has remarkable similarities to the testicular dysgenesis syndrome in humans. Concentrations of BPA in the foetal mouse within the range of unconjugated BPA levels observed in human foetal blood have produced effects in animal experiments. Finally, thyroid hormones are essential for normal neurological development and reproductive function. Human body burdens of these chemicals are detected with high prevalence, and concentrations in young children, a group particularly sensitive to exogenous insults, are typically higher, indicating the need to decrease exposure to these compounds.

Figure 1.

Bisphenol A (BPA) concentration in water placed into food cans that had contained different products. Two or three different brands of each product were examined. The cans were emptied, cleaned and rinsed with water that did not contain detectable levels of BPA. The 10 cans and a single new reusable ‘microwave safe’ polycarbonate food container were filled with HPLC-grade water and heated to 100°C for 24 h. Bisphenol A was extracted and analysed by HPLC with CoulArray detection (limit of detection was 0.01 ppb). Negative controls in glass bottles gave undetectable levels of BPA. Spiked samples in glass containers gave >95 per cent recovery. Significant leaching of BPA occurred from each type of product tested.

Figure 2.

Number of Sertoli cells per tubule cross-section in adult male offspring (F1) on PND 110 and flow cytometry analysis of testicular cell population on the basis of their DNA ploidy in adult rats on PND 140. Gravid female rats were administered per gavage either vehicle (control) or 60 or 300 µg BDE-99 (kg bw)⁻¹ (PBDE-60 or PBDE-300) on gd 6. A fourth group received 5 mg 6-n-propyl-2-thiouracil (PTU) l⁻¹ in drinking water from gd 7–21. ANOVA followed by Dunnett t-test, *p < 0.05.