Microplastics linked to cancer, infertility and lung disease
A scientific review of the effect of microplastics has found they cause infertility and are associated with colon cancer.
A groundbreaking scientific review of the effect of microplastics on human health has found the environmental contaminants cause male and female infertility, are associated with colon cancer, and also cause chronic lung diseases.
The review of 3000 studies conducted by the University of California and led by University of Sydney researcher Nick Chartres examined every available study on the health effects of microplastics, including on the respiratory, digestive and reproductive systems. Microplastics are smaller than a grain of rice and are ubiquitous in the air and waterstreams. They are contained in the 460 million metric tonnes of plastic produced by corporations. There are documented examples of harms caused by exposures, but until now there had been a paucity of research evaluating their impacts on human health.
Dr Chartres led a systematic review which used a gold-standard method of analysis endorsed by the US National Academy of Sciences to analyse thousands of studies. The review builds on a report the researchers worked on last year with the California State Policy Evidence Consortium. Many of the studies were based on animals, but the researchers said the conclusions likely applied to humans as well.
The peer-reviewed systematic review published in the journal Environmental Science & Technology concluded that although evidence gaps remain, there is evidence to support suspicions that microplastics harm human reproduction and digestive and respiratory health, with a suggested link to colon cancer. It recommended that all governments should take immediate action to mitigate exposure to microplastics.
The review examined studies into three polymer types: polystyrene, polyethylene and polypropylene, as well as a major secondary source of microplastics, tyre particles that are thrown into the air when tiny pieces are shorn from car tyres during driving.
There was strong evidence that microplastics affected fertility in men and women. Using the key characteristics of reproductive toxicity, the scientists found that the more key characteristics of cancer or reproductive toxicity were found to exist in subjects studied, the more likely their microplastics exposure.
They said the body of evidence linking the likelihood of adverse effects on sperm quality and immunosuppression to microplastics exposure was high, however the evidence was downgraded to establishing a “presumed” link because of the sample size and number of studies in the systematic review.
Evidence of harms caused by microplastics to female follicle and reproductive hormones, digestive outcomes including cell death and chronic inflammation, respiratory outcomes including impaired pulmonary function, lung injury and oxidative stress were rated as of moderate quality, concluding that microplastics exposure is “suspected” to adversely affect these bodily processes and systems. The scientists said that exposure to microplastics was “unclassifiable” for birth outcomes and gestational age in humans based on the low and very low quality of evidence examined.
“We looked across these systems for reproductive, digestive and also respiratory effects,” said Dr Chartres. “What we found was these really consistent effects, organ-level effects. We also saw a lot of biological changes. And a couple of these most important ones we saw was chronic inflammation in the small intestine, in the colon, but also in the lung. Those two markers of chronic inflammation, those two system, are predictors of cancer.”
Dr Chartres said that the US Environmental Protection Agency are the leading authority globally on evaluated chemicals and regulate chemicals based on animal data. As well, the International Agency for Research on Cancer also makes conclusions about whether substances are carcinogenic based on animal data. That is the case because scientists cannot ethnically expose humans to potentially dangerous contaminants. Therefore the animal studies included in the current research were legitimate to use as the basis to draw conclusions.
“What we need to do is ban all single use plastics,” Dr Chartres said. “We need to ban all non-essential plastics, because unless it can be demonstrated that they are absolutely essential for society to function, say for something like a medical device, we need to be getting plastic out of our environment as soon as we can.
“We need people to be aware of the link between fossil fuels and petrol and plastics in our environment, because if we don’t get people to understand that, in 20 or 30 years’ time we’re going to have a full raft of health effects seen in humans and the issue is going to be that we can’t get these plastics out of our environment.”
