Even small doses of poisonous chemicals in the environment pose a substantial risk to cardiovascular health, according to a report in the August 29 th edition of The BMJ, led by scientists at the University of Cambridge. The scientists have also questioned the omission of environmental risk factors such as toxic metal contaminants in foods and water from the latest World Health Organization report on non-communicable diseases (NCDs).
Filter bed beside Afon Rheidol Water draining from an adjacent disused silver-lead mine is passed through these filter beds so as to allow the toxic heavy metals to settle out, thereby reducing pollution of the river. (Image credit: geograph.org.uk)
In the last few decades, exposures to environmental toxic metals such as cadmium, copper, lead, arsenic, and mercury, have become a universal public health concern. Although frequently naturally occurring, these contaminants have entered into water supplies and, via irrigation, into the food chain. For instance, in Bangladesh, deep wells were dug up in the Ganges Delta to draw water clear of viral and bacterial pathogens, but this unintentionally resulted in the exposure to toxic metals.
The concern, mostly, has been on the carcinogenic or toxicity properties of the metals, especially at high doses. However, there is increasing proof to indicate that heavy metals may have other harmful effects on health—including cardiovascular disease such as stroke and heart disease—even at minor levels of exposure, which might be widespread in many regions of the world, including the US and the UK.
To understand the available evidence, a team led by scientists at Cambridge’s Department of Public Health and Primary Care performed a methodical review and meta-analysis of published studies covering 350,000 unique participants from 37 countries.
The results of the research revealed that exposure to arsenic, cadmium, lead, and copper—but not mercury - was related to an increased risk of cardiovascular disease and coronary heart disease.
It’s clear from our analysis that there’s a possible link between exposure to heavy metals or metalloids and risk of conditions such as heart disease, even at low doses - and the greater the exposure, the greater the risk. While people shouldn’t be overly worried about any immediate health risk, it should send a message to policymakers that we need to take action to reduce people’s exposure.
Dr Rajiv Chowdhury, First Author
Globally, those at maximum exposure of lead, cadmium, arsenic, and copper were about 30% to 80% more probable to get a cardiovascular disease compared to those at lowest exposure.
The scientists state the report is crucial, as it emphasizes the need to face this environmental and public health issue, one which disproportionately impacts people in middle and low income countries, though may still impact those in higher income countries. Interventions need not be expensive, they stress; for instance, economical, scalable technologies (for example, environmentally-friendly water filters) or behavioral interventions (for example, rinsing practices of vegetables and rice before cooking) are presently being tested to lower exposures at the household level.
Furthermore, in a letter published at the end of June, Dr Chowdhury and colleagues expressed their discontent that the previous WHO report by the Independent High-Level Commission on non-communicable diseases published in June did not cover exposure to heavy metals as a chief contributing factor.
Writing in the Lancet, the authors said:
“Unfortunately, this globally important report had a major omission: recognising the detrimental role of environmental risk factors, beyond the conventional behavioural factors (tobacco and alcohol use, physical inactivity, and unhealthy diet), in enhancing global NCD burden and health inequality.”
Dr Chowdhury and colleagues recently also received £8.1 million from the UK Research Councils’ Global Challenges Research Fund to form a long-term program (called CAPABLE) to further study environmental factors of cardiovascular diseases and to help inform preventative policies.