health effects of metal pollution

In a recent study, scientists estimated exposure to metallic particles in air pollution and its link to mortality rates.

Air pollution can no longer be considered as a mere nuisance but is now a serious health hazard. The WHO estimates that outdoor air pollution was the cause of 4.2 million deaths in 2016 alone. The United States Environmental Protection Agency has listed airborne particulate matter as being directly linked to health issues including heart and lung disease, aggravated asthma and increased respiratory problems such as coughing and difficulty breathing.

Metals make up a major component of particulate matter including some that are listed as carcinogens by the International Agency for Research on Cancer. The presence of metals in the air can be traced to natural sources such as soil dust or due to man-made sources such as factories or road traffic. Studying the effect of atmospheric metals is a challenge for researchers due to the difficulty in monitoring and measuring pollutants over large areas and over a long period of time. A collaborative effort by scientists from France, Canada, and Spain has resulted in an innovative method to combine biomonitoring with epidemiological data. Their results were published in the journal Environment International. The researchers used information from the GAZEL cohort in France, including vital stats data collected over a 20-year period. The data also included the geographical location of participants and over 11,000 participants living in rural France were included in this study. The researchers linked this data to metal concentrations in moss samples collected by the BRAMM bio-vigilance program over 12 years. Using geostatistical methods and mathematical modeling the researchers were able to estimate mortality rates linked to airborne metallic pollutants.

Their findings suggest an increased risk of death by natural causes with increased exposure of metals in the air that arise from man-made sources. These metals include cadmium, mercury, lead, and zinc. In contrast, they did not find any evidence linking exposure to metals arising from the earth’s crust, such as copper, to natural-cause mortality.

Delving deeper into their analyses, the researchers found that mortality rates linked to metallic air pollution tend to be higher amongst sub-populations including women, non-smokers, and those living within 1000 meters of major roads. Additionally, they also report higher incidences of cardiovascular and respiratory deaths than deaths due to natural causes. The authors caution that their analyses with the sub-population mentioned above are not statistically rigorous and the linkages could be co-incidental until further studies show them to be otherwise.

The results do suggest that the model developed by this group of scientists, led by Dr. Bénédicte Jacquemin, is a valid method to assess exposure to atmospheric pollution and its link to mortality rates. As Dr. Jacquemin explains, “These findings support our hypothesis that moss bio-monitoring can be a good complementary technique for identifying the toxic components in suspended particulate matter.” She further described the significance of their results, “Our results indicate that the metals present in the airborne particulate matter could be a key component in the effects of air pollution on mortality[.] It is important to bear in mind that the people we included in this study live in rural areas far from major urban and industrial centers and road networks. This means that they are very likely to be exposed to lower levels of air pollution than people living in urban environments, which gives us an idea of the seriousness of the health effects of air pollution, even at relatively low levels of exposure.”

Written by Bhavana Achary, Ph.D


Reference: Lequy E, Siemiatycki J, Leblond S, Meyer C, Zhivin S, Vienneau D, de Hoogh K, Goldberg M, Zins M, Jacquemin B. Long-term exposure to atmospheric metals assessed by mosses and mortality in France. Environ Int. 2019 May 22;129:145-153.

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