Phthalates (also known as phthalic acid esters, or PAEs) are used as plasticisers in many consumer products, such as plastics and polyvinyl chloride (PVC), and as solvents in adhesives, cosmetics and paints. Phthalates are one of the most common organic contaminants in the environment, but data about human exposure to them are limited. This article reviews the sources, levels and distribution of phthalate contamination in China, and compares the results with other countries.
China is a major producer and user of phthalate-containing products, and such products are used ubiquitously worldwide. As a result, phthalates are a common environmental contaminant, and human exposure is unavoidable. But how much we are exposed to is not well known, especially in China.
The health effects from phthalate exposure are also poorly defined. Several studies have shown that phthalates are endocrine-disrupting chemicals, which have negative effects on human health. Some, such as di-(2-ethylhexyl)phthalate (DEHP), are possible carcinogens. Other ill health effects associated with phthalate exposure include reproductive toxicity and metabolic disorders.
A number of countries have classified phthalates such as DEHP as ‘priority pollutants’. Many countries have banned the use of DEHP in materials, but many developing countries still use it.
How are people exposed to phthalates?
There are many routes for exposure to phthalates, which is not surprising given their widespread use. People can be exposed to phthalates by breathing contaminated air or drinking polluted water. Phthalate-contaminated soil also offers several sources of exposure, and people may be exposed internally through plastic-based medical devices. Babies can be exposed to phthalates through breastmilk.
This article outlines the common exposure routes and sources of contamination in China.
In China, increased levels of phthalates are found in the air around facilities used for plastic waste recycling and municipal waste incineration. e-waste is particularly high in phthalates. Recycling and incineration processes release phthalates into the air, water and soil, thus also leading to soil and water contamination.
Dust and personal product contamination
Phthalates are found in many common household and personal products in China, such as PVC flooring, vinyl wallpaper, ceiling materials, hair gels and sprays, cosmetics (including nail polish), body lotions, fragrances and deodorants. Such products can release phthalates that end up in dust, and dermal exposure can occur through any substance that is directly applied to the skin.
Studies have shown that phthalates are widely found in both urban and agricultural soils in China. Several practices can lead to phthalate soil contamination:
- Urbanisation and industrialisation – Phthalates are widely used in industrial processes and products. From these sources, phthalates can be released to the environment during all stages of production and product degradation.
- Plastic film used in agriculture – Mulching with plastic film is common agricultural practice, especially in arid or semi-arid regions, and phthalates are a major component of plastic films. Phthalates can end up in the soil by leaching, migration and abrasion from the plastics.
- Fertiliser application – Applying fertiliser is another common agricultural practice, and China is a world leader in the use and production of fertilisers. Phthalates are a common component of synthetic fertiliser.
- Wastewater irrigation – Severe water shortages in China have led to irrigation with wastewater. Wastewater contains several contaminants, including phthalates.
- Sewage sludge application – Sewage sludge is used worldwide as a fertiliser and soil amendment. However, sewage sludge contains organic contaminants, including phthalates.
Food and water contamination
Food and water contamination is the most common method of exposure for people in China – called dietary exposure. Phthalates can bioaccumulate in food sources higher in the food chain. Further, plastic food storage containers contain phthalates, which could leach and migrate into the food or liquid. Contaminated water can lead to contaminated seafood. Finally, crops grown in phthalate-contaminated soil can take up phthalates, which in turn can be eaten by humans.
Plastic-based medical devices, such as those used in blood transfusions and haemodialysis, could be a source of phthalate contamination.
How serious is phthalate contamination in China?
Relative to other countries, the phthalate contamination of soil, water and air in China is moderate to severe, depending on the exposure route. There are not a lot of data available, however.
As mentioned, exposure through diet is common, and an important route for phthalate exposure in China. In addition to eating contaminated plants, such as vegetables and cereals, soil itself can be ingested and inhaled. Aquatic foods are also highly contaminated with phthalates in China, especially fish from the Pearl River Delta.
In China, the levels of phthalate exposure vary from region to region. This variation could be real, but – because there are so few data from some areas – it is more likely due to estimation errors and other biases. For example, places of intense manufacturing, such as the Pearl River Delta, have been studied more than other regions, thus possibly skewing results.
As an example of the national variance in levels of soil contamination, Figure 1 shows the average concentrations of dibutylphthalate (DBP) and DEHP in samples taken from across China. For reference, the Pearl River Delta is in the Guangdong, Hong Kong and Macau regions.
Other variances in phthalate distribution patterns could be due to temperature differences (for air contamination), and seasonal differences and depth of sample (for soil contamination).
How do exposure and source levels in China compare with other countries?
Indoor levels of phthalates (from dust and personal care products) in China are comparable to other Asian countries, and moderate compared with other parts of the world. Air and foodstuff contamination in Chinese cities are low compared with other global cities. The levels of phthalates in Chinese soils are at the high end of the global range. China also has a high dietary exposure compared with other countries, but with a lot of regional variability.
Although some phthalate contamination sources and exposure levels in China were around the global average, there are not a lot of data available on which to base solid conclusions. Also, phthalate use is increasing, and the human exposure trend is unknown. Phthalate contamination is widespread and could be getting worse, not better.
What questions still need to be answered?
In China, we need to examine regional discrepancies in phthalate exposure levels and collect more samples, to ensure that all segments of the population are represented in studies. Does exposure depend on income, age or area of residence? Studies also need to include subpopulations – for example, do workers at recycling plants have higher exposure levels than other subpopulations?
In addition, the health effects of phthalate exposure and routes of exposure need to be determined, again in different populations. Does the health effect depend on the route of exposure and the type of phthalate? Do different types of phthalates have different human exposure routes?
Until some of these questions are answered, it will be difficult to assess the health of the Chinese population as a result of phthalate contamination. More information is also needed about the extent of phthalate contamination across China. Making phthalates a research priority could lead to changes to manufacturing policies and to remediation strategies.
This article was based on 2 reviews:
- Lü H, Mo CH, Zhao HM, et al (2018). Soil contamination and sources of phthalates and its health risk in China: a review. Environ Res 164:417–429.
- Wang W, Oi Wah Leung A, Chu LH, Wong MH (2018). Phthalates contamination in China: status, trends and human exposure – with an emphasis on oral uptake. Environ Pollut 238:771–782.