Plastics and their impacts on human health
Plastics are detrimental to human health primarily because of the chemicals used in their production and manufacture. Chemicals are used to change the properties of plastics whether to soften them such as in cuddly toys, harden them in the case of plastic bottles or change the colour of plastics. There are three key paths through which humans are specifically exposed to such toxins: our general environment i.e. through air and water, through food such as fish, or direct contact with plastic products.
Most plastics per se have some impact on human health to a greater or lesser extent. Specific chemicals that have raised serious concern as causing potential harm to humans are phthalates (Diethylhexyl phthalates – DEHP), BPA (Bisphenol A), and heavy metals such as lead, cadmium and mercury (albeit plastics is a small source of such metals to our environment). The toxins leach into our environment over the service life of the plastic object and we unknowingly “consume” them through direct contact with plastic or through food that has been exposed to plastics. Additionally micro-plastics in the oceans attract certain chemicals such as persistent organic pollutants (POPs) such as DDT which become ingested by fish, accumulate through the food chain, and end-up consumed by us (see UNEP).
These toxins are ubiquitous in our environment: 95 percent of us have detectable levels of phthalates in our urine ( see Huffington Post), while a 2011 study that investigated the number of chemicals pregnant women are exposed to in the U.S. found BPA in 96% of women (see Wikipedia on BPA). While heavy metals such as mercury are found at such levels in certain fish and shellfish that pregnant women and children are recommended to only eat restricted amounts (US EPA). Depending on the toxin in question health implications include cancer, such as breast cancer, endocrine disruption (influencing how are hormones function), impacts on the nervous system and mental development, behavioural issues such as ADHD and allergies (see list below).
The extent of regulation of plasticisers and plastic additives depend on the use of the plastic i.e. if it comes into contact with with children or food restrictions generally apply. However, there is disagreement about the extent of regulation needed. For example, both phthalates and BPA are still under debate as to whether their potential for harm is significant enough to justify further regulation.
Since 1999, use of some phthalates has been restricted in children’s toys in the European Union and in plastics that have contact with food. The restriction states that the amount of phthalates may not be greater than 0.1% mass percent of the plasticized part of the toy. These phthalates are allowed at any concentration in other products and other phthalates are not restricted. Denmark is trying to ban the four most harmful phthalates arguing that there is a “cocktail effect” due to exposure from many sources but this was turned down on the grounds that current regulation is resulting in the reduction of phthalates in plastics and therefore reducing risk. Denmark still disagrees. (see Danish Environmental Agency)
In January 2011, the European Commission adopted Directive 2011/8/EU, prohibiting the use of BPA for the manufacture of polycarbonate infant feeding bottles. But BPA is permitted in use of other plastics that come into contact with food. For example, the majority of food cans in the UK are lined with a plastic coating containing bisphenol A (BPA) (see Independent newspaper). BPA is still considered low risk, however, in January 2014 the Commission recommended that the current tolerable daily intake (TDI) be lowered from its current level of 50 µg/kg bw/ day (or 0.05 mg/kg/bw/day) to 5 µg/kg bw/day (0.005 mg/kg/bw/day) (European Food Safety Authority – EFSA) . Many companies have ceased using BPA in polycarbonates plastics but alternatives aren’t necessarily safer (see Wikipedia). The US National Toxicology Program (NTP) is currently carrying out research into BPA but currently there are no restrictions. According to the European Environment Agency’s report discussing the precautionary principle, whether BPA is actually safe is still a moot point:
The ‘late lesson’ with respect to BPA is the ‘same old story’ of putting a chemical into widespread use without understanding its health implications, and then trying to resolve public health questions while facing the intense pressure of serious economic consequences. The competing urgency of public health and economic stakes puts the scientific process under enormous pressure. In this perspective the story of BPA resembles those of asbestos, polychlorinated Biphenyls (PCB) and Diethylstilboestrol (DES).
Generally, plastic food packaging contains low concentrations of metallic compounds but heavy metals such as lead and cadmium have been detected recurrently. Sources of such metals in plastics are impurities originating from inorganic pigments and stabilisers. In the Europe the EU Directive 94/62/EC (amended by 2004/12/EC) on Packaging and Packaging Waste sets out a maximum limit of 100 mg/kg for all Pb, Cd, Cr (VI), Cd and Hg in packaging materials (see WHO) which is the same in many states in the US (see Plastic News).
As mentioned in the previous article about plastic litter in the marine environment, studies show that micro-plastics ingested by marine animals can cause accumulation of certain chemicals resulting in physiological impacts. The concern is whether micro-plastics will increase chemical uptake and accumulation throughout the food chain increasing our exposure to such chemicals through our food. This pathway of exposure is yet to be explored in great depth.
The challenge in determining the impacts of toxins in plastics to human health is that the link between exposure and effect is complicated. Rolf Halden, Associate Professor in the School of Sustainable Engineering, Arizona State University, concluded in his study of plastics that it is almost impossible to determine the exact health effects of plastics on humans because plastic contamination is globally spread; we are all subjects to exposure. But the evidence undeniably shows that plastics are affecting our environment and our health (Medical News Net).
Next: Ultimately, plastic waste needs to be minimised and managed more effectively. ICIS will look next at examples where this is happening – whether it be more recycling, substitutes to plastic or alternatives that bypass the need for plastics altogether.
Overview of key chemicals related to plastics and their health implications
Phthalates - DBP (di-n-butyl phthalate), DEP (diethyl phthalate), DEHP (di-(2-ethylhexyl) phthalate or bis (2-ethylhexyl) phthalate), BzBP (benzylbutyl phthalate), and DMP (dimethyl phthalate).
Uses: Present in PVC plastics typically used for various containers e.g. for food and beverages, and hard packaging, medical tubing, and bags, toys, traces have been found in PETE plastic bottles. (phthalates are not only used as plasticisers but also in many cosmetics so the source of phthalates to our environment is much greater than plastics alone)
Exposure: Direct contact with plastics, bottled water, tap water, air and food
Potential health effects: Endocrine disruption, cancer, obesity, ADHD, allergies, diabetes…
Legal status: Restrictions in toys and infant products in Europe. Voluntary withdrawal in US from products that can be placed in child’s mouth.
Bisphenol A (BPA)
Uses: Containers such as baby and water bottles, sports equipment, CDs, and DVDs, lining water pipes, coatings on the inside of many food and beverage cans, thermal paper such as sales receipts.
Exposure: Human exposure is through diet (leaching from food and beverage containers), exposure can also occur through air and through skin absorption.
Potential health effects: An endocrine disruptor that can mimic estrogen having potentially adverse effects on the liver and kidney and effects on the mammary glands as well as heart disease, diabetes and child behaviour.
Legal status: In Europe many countries have banned use of BPA in baby products such as baby bottles and restrictions on amount of BPA in plastic products are in place. Many companies have voluntarily decided to stop using BPA in their products. But risk is still considered low in Europe.
Uses: Lead, cadmium, chromium, mercury, bromine, tin, antimony and other heavy metals are or have been added to polymers as pigments, fillers, UV stabilizers, and flame retardants (source).
Exposure: During waste disposal either by incineration or by placing it in a landfill, toxic metals released from plastics can enter atmosphere or leach into soil (source).
Potential health effects: Children’s exposure primary concern as certain metals cause impacts on nervous system (lead), mental development (mercury) and kidney disfunction (cadmium) amongst many other effects caused by other heavy metals (source).
Legal status: Maximum allowable concentrations of toxic metals in plastics related to food packaging are in place.