The news made for an alarming headline recently: Research showed that common chemicals in plastics were associated with 350,000 heart disease deaths across the world in 2018.
The statistic came from a study published in the journal eBioMedicine. The authors, a group of researchers at New York University’s Grossman School of Medicine, estimated that roughly 13 per cent of cardiovascular deaths among 55- to 64-year-olds worldwide that year could be attributed to phthalates, which are used in food packaging, shampoo, toys and more.
Research on the effect of phthalates on cardiovascular disease is still emerging, but their link to metabolic risk factors like obesity suggests they could play a role in heart disease.
While experts agree that phthalates are harmful, they cautioned that the study relied on complex statistical modelling and a series of assumptions and estimates that make it difficult to determine how many deaths might be linked to the chemicals.
“This is an early step of trying to understand the magnitude of the problem,” said Dr Mark Huffman, a cardiologist and a co-director of the global health centre at WashU Medicine in St Louis. But, he added, there’s a need for far more studies to understand the relationship between phthalates and heart health, and what other factors might come into play.
THE BACKGROUND
Phthalates are found in personal care products like shampoos and lotions, as well as in food containers and packaging. It’s possible to ingest them through food, absorb them through the skin from products containing them or breathe them in as dust.
Studies have shown that phthalates are endocrine disrupters, meaning that they can interfere with our hormones. They have been associated with negative effects on reproductive health, pregnancy and birth issues.
Some studies have shown an association between phthalates and cardiovascular disease, but there isn’t strong evidence to show that the chemicals directly cause heart issues, said Sung Kyun Park, a professor of epidemiology and environmental sciences at the University of Michigan School of Public Health.
There is evidence that phthalates increase the risk of metabolic disorders like obesity and Type 2 diabetes, which can cause cardiovascular disease.
One way phthalates may do this is by increasing oxidative stress – cell and tissue damage that happens when there are too many unstable molecules in the body – and by promoting inflammation, said Dr Leonardo Trasande, senior author of the new paper and a professor of paediatricsand population health at NYU.
THE RESEARCH
In the latest study, researchers attempted to quantify global cardiovascular deaths attributable specifically to one type of phthalate, known as DEHP. One of the most widely used and studied phthalates, DEHP is found in vinyl products including tablecloths, shower curtains and flooring.
The researchers relied on estimates from previous research for several measures: Phthalate exposures, the risk of such exposures on cardiovascular deaths and the global burden of cardiovascular disease. They then calculated the share of deaths attributable to phthalate exposures in different countries, Dr Trasande said. The Middle East, South Asia, East Asia and the Pacific accounted for nearly three-quarters of these deaths.
THE LIMITATIONS
This was an observational study that showed a correlation between estimated exposure to the chemical and disease at the population level. Experts said that the methods used were not unusual for studies that model global disease, but that such studies come with caveats.
For example, Dr Huffman said, the estimates from the literature that the authors relied on in their calculations may themselves have incorporated some bias or confounding variables, such as socioeconomic status or dietary behaviours, that could relate both to plastic exposure and to cardiovascular disease rates.
“A pretty important part of the result of the model is what you put into the model,” Dr Huffman said.
The study also relied on an earlier analysis by Dr Trasande to estimate the risk of cardiovascular death from phthalate exposure, after controlling for other known risk factors. But that paper only examined US patients, which means it might not be possible to generalise the results to a global population, where dietary habits, cigarette smoke exposure, physical activity and other cardiovascular risk factors may vary.
WHAT’S NEXT
What’s clear from the study, experts said, is that we need more research on phthalate exposure and the associated health risks. Though it would be ethically impossible and impractical to do a classic randomised trial, in which one group of people were exposed to phthalates and others were not and they were followed for many years, other types of studies could help more clearly establish a link.
One way, Dr Park said, would be to have researchers recruit a large, representative sample of patients, measure their levels of exposure and follow them for years, perhaps until death. Dr Huffman suggested it would also be worthwhile to try out strategies that might reduce exposure levels and then measure any changes in health outcomes.
Tracey Woodruff, director of the programme on reproductive health and the environment at the University of California, San Francisco, said that despite the uncertainties in the estimates of the current paper, it is clear that phthalates can increase the risks of preterm birth, reproductive issues and metabolic disorders. To her, the findings only add to the list of reasons to reduce the amount of phthalates in the supply chain.
By Nina Agrawal © The New York Times Company
The article originally appeared in The New York Times.
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