Canada declares bisphenol A a ‘dangerous substance’: Questioning the safety of plastics

The Canadian government has recently taken a bold step in becoming the first country to declare bisphenol A (BPA) a ‘dangerous substance’, thereby raising strong consideration for its banning (1). It is a synthetic petroleum-based chemical present in a variety of hard plastic products (eg, baby bottles, food storage containers, plastic drinking bottles, food can linings and dental sealants), and has the potential to leach into food. Leaching is accelerated particularly by heating (2). To date, no longitudinal human health effect epidemiological studies have been published. BPA is an endocrine disruptor and may mimic the hormone estrogen. A recently published review (3) of the literature identified 115published animal studies, 81% of which found significant effects at low levels of exposure to BPA, meaning that the effects were observed when using less than 50 mg/kg of body weight/day – the accepted ‘no observed adverse effect’ level for BPA (3). Approximately one-third of those studies found effects when testing concentrations below 50 μg/kg/day. The described adverse effects are related to endocrine disruption (estrogenic effects) and include (4):

• Stimulation of mammary gland development in females and early onset of puberty (eg, experiments performed on pregnant mice exposed to 0.025 μg/kg/day and 0.250 μg/kg/day or 2.4 μg/kg/day to 500 μg/kg/day of BPA, respectively).

• Decreased testosterone levels and other hormonal changes (eg, male rats born to mothers exposed to 2.4 μg/kg/day dose of BPA).

• Decreased sperm production (eg, adult male rats born to mothers who were exposed during pregnancy to 20 μg/kg/day dose of BPA).

• Alterations in immune functions (eg, male offspring of pregnant mice fed 30 μg/kg/day dose of BPA).

• Increase in prostate size (eg, adult male rats whose mothers were exposed during pregnancy to 2 μg/kg/day dose of BPA).

• Neurobehavioural effects with impaired learning, increased aggressiveness and hyperactivity (eg, rat offspring prenatally exposed to BPA that was administered orally to mothers throughout gestation at a dose of 40 μg/kg/day).

Other animal studies describe chronic effects such as stimulation of prostate cancer cells (5) and changes in mice breast tissue resembling early stages of breast cancer (6,7).

In the United States, the Centers for Disease Control and Prevention has published urinary surveys (8) detecting BPA in 95% of adults sampled. Further studies of BPA in the blood of pregnant women and in umbilical cord blood reveal levels similar to those in animals causing the changes described above (9,10). BPA has been linked to chromosomal errors in mice at low levels of exposure leading to spontaneous miscarriages and birth defects (11). BPA has become one more environmental reproductive toxin, and concerning evidence is accumulating (12).

In the absence of longitudinal studies in humans, and due to potential for increased human and environmental exposures (13), Health Canada, exercising precaution, identified that BPA satisfied their criteria for moving toward a ban (14).

One may argue that the level of evidence for BPA causing harm to human health is extremely limited, and yet Health Canada has taken a definitive step toward its banning. Those that practice evidence-based paediatrics may be initially bewildered by this action. Others may support this precautionary approach as definitive proof of harm may be decades away. Others may still question the availability of a safer alternative. Currently, we are reassured that safer alternatives exist both for baby bottles and for food containers – these being the glass or ceramic variety – despite risks of injuries due to breakage.

Although direct extrapolation from animal studies cannot be made to humans, many factors are taken into consideration in the risk assessment and management process.

Scientific evidence, public perceptions, economic implications and safer alternatives are examples of factors that may come into play. Media focus on environmental issues has increased public awareness for children’s health and environment concerns, and this may influence trends in policies. BPA removal from consumer products offers an opportunity for reducing human body burdens, while awaiting epidemiological human evidence. Currently, BPA exposure from sources other than consumer products, especially in children, is limited (14).

CHILDREN’S SPECIAL VULNERABILITIES

Children have special vulnerabilities to environmental hazards due to their unique physiology, behaviours, routes of exposure and longer life expectancy. Identifying substances with potential for harm to the fetus and child, in which the risk from adult exposure may be much lower, is a step toward protection not only of children but the adults they will grow up to be.

The current federal government announced a $300 million plan to address a large number of potentially harmful chemicals currently present in regular consumer products (15). Are we seeing the beginning of a process that may lead to major changes in how we deal with environmental chemicals in Canada? (16).

Because BPA is only one of very many petroleum-based chemicals in various types of plastics to which newborns and children are exposed, should we be paying more attention to others (eg, phthalates, which are widely used in consumer products to soften the plastic polyvinylchloride used in toys, intravenous tubing, transfusion bags, medical gloves, as well as food packaging, cosmetics, lotions and pharmaceuticals). Di-(2-ethylhexyl) phthalate (DEHP) has been associated with toxicity to the developing endocrine and reproductive systems with an increased incidence of hypospadias and cryptorchidism in animals (17). DEHP has been studied in humans identifying similar adverse effects of DEHP on male reproductive function. Recent attention in human studies has focused on decreased anogenital distance, which is a well-described marker of decreased androgenization in animal studies for male newborns (18). Phthalate metabolites identified in young children are thought to result from both sucking on plastic toys and application of child care products to the skin (19). A further source of exposure may be through food products contaminated during processing and packaging (20).

BPA and DEHP at the levels of exposure discussed in the present commentary may have no harmful effects on adults in the short term; however, exposures of pregnant women and young children may have far-reaching consequences both in the shorter and longer term.

Advice to our patients should include reducing children’s exposures to BPA and phthalates by seeking out and avoiding polycarbonate plastics and polyvinyl chloride or vinyl (Figure 1). Caution regarding phthalate absorption by young children from lotions and shampoos needs to be exercised. Avoidance of microwaving or otherwise heating plastic bottles or containers used for milk or food needs to be reinforced.

Figure 1).

Which plastics to use and which to avoid. HDPE High-density polyethylene; LDPE Low-density polyethylene; PETE Polyethylene terephthalate; PP Polypropylene; PS Polystyrene; PVC or V Polyvinylchloride. Adapted from reference 22

Medical exposures through intravenous tubing, nasogastric tubes, umbilical catheters and dialysis need to be addressed centrally. In 2002, a Health Canada expert advisory panel on DEHP in medical devices issued a final report (21) recommending the use of DEHP-free medical devices where available, especially for newborns. The issue of safety of children in Canadian hospitals is receiving attention as well as resources. The risk to children from plastics in medical devices and other potential sources of exposure needs to be addressed.

Figure 1 identifies which plastics to avoid by looking at product labels and identifying the symbols shown. We have included symbol 6 or polystyrene foam for completeness, even though this is not discussed in the paper. These symbols have been widely used by manufacturers to identify product content.

The subject of safer plastics is controversial with many intricacies. Until we have prospective longitudinal human health studies, many questions will remain unanswered.