Atmospheric Mercury Concentration Increases by Sevenfold Due to Human Emissions; Experts Warn of Potential Environmental Impact

Mercury is a naturally occurring element known for being a toxic pollutant that can harm human health. It is introduced into the environment naturally from volcanoes, from the burning of fossil fuels, and by evaporation of ocean water. A new study reveals that human activities have increased the concentration of potentially toxic mercury in the atmosphere.

Threat From Human Emissions

Researchers from the Harvard John. Paulson School of Engineering and Applied Sciences (SEAS) investigated the amount of mercury put into the atmosphere by volcanoes. Their study uncovered humanity's contribution to the emission of atmospheric mercury since the beginning of the modern era.

Led by Professor Elsie M. Sunderland, the scientists developed a novel method of estimating the amount of mercury emitted annually from volcanoes, the largest single natural emitter of the toxic element. Together with a computer model, they used that estimate to reconstruct pre-anthropogenic levels of mercury in the atmosphere.

It was estimated that before humans began releasing mercury into the atmosphere, it only contained an average of 580 megagrams of the toxic metal. In 2015, however, independent research estimated atmospheric mercury concentration was about 4,000 megagrams. This means that human activities have increased the concentration of atmospheric mercury sevenfold since the beginning of the modern era in the 1500s.

According to Sunderland, understanding the natural mercury cycle driven by volcanic activities sets a baseline goal for policies that aim to reduce mercury emissions and allows experts to understand the full impact of human activities on the planet.

Measuring atmospheric mercury is challenging because there is not much of it, despite its impact on human health. In every cubic meter of air, there could only be one nanogram of mercury, making it virtually impossible to detect by satellite. To address this challenge, the research team used another chemical as a substitute. For this study, the researchers used sulfur dioxide, a significant component of volcanic emissions.

The team used a compilation of mercury to sulfur dioxide ratios measured in volcanic gas plumes; then, they reverse-engineered the amount of mercury that could be attributed to volcanic eruptions. Afterward, they used the GEOS-Chem atmospheric model to simulate how mercury from volcanic eruptions moves across the Earth.

It was discovered that as mercury mixes into the atmosphere, traveling long distances from its injection site, volcanic emissions are directly responsible for only a few percent of ground-level concentrations in most parts of the planet.

Dangers of Mercury Exposure

Mercury exists in different forms, and humans are exposed to each in various ways. The most common method people are exposed to this toxic element is by eating fish that contains methylmercury. Other modes of exposure include using or breaking products that contain mercury. Human activities contributing to mercury emissions include mining, waste incineration, and coal-fired power plants.

The World Health Organization considers mercury one of the top 10 chemicals of major public health concern. Exposure to this element, even in small amounts, can cause serious health problems, particularly in the immune, digestive, and nervous systems. It can also harm a person's eyes, skin, kidneys, and lungs.