Mercury promotes blood clots, which increases heart disease risk.

Jun 22, 2010

Lim K-M, S Kim, J-Y Noh, K Kim, W-H Jang, O-N Bae, S-M Chung and J-H Chung. 2010. Low-level of mercury enhances procoagulant activity of erythrocytes: A new contributing factor for mercury-related thrombotic disease. Environmental Health Perspectives http://dx.doi.org/10.1289/ehp.0901473.

Synopsis by Jennifer F. Nyland

A research team describes the likely way mercury affects red blood cells and increases the risk of heart disease.

Researchers have determined that exposure to low levels of mercury can encourage clotting of red blood cells, a dangerous condition called thrombosis that contributes to cardiovascular disease.

In short, the research shows that red blood cells, when dying after exposure to mercury, release proteins that encourage blood cells and platelets to clot and clump together – or coagulate – inside vessels. The increased clots can worsen existing cardiovascular disease and raise its risk in others.

Mercury is a global environmental contaminant with almost universal human exposure. The metal is linked to an increased risk for developing cardiovascular disease. Its association with one of the top human diseases has vast public health implications.

The laboratory study is the first to identify the specific cell responses that may play a role in why exposure to the metal elevates the risk of heart and circulatory disease. The results validate that changes seen in red blood cells exposed to very high levels of mercury also occur in cells exposed to low levels of the metal.

Although mercury occurs naturally, mining, power generation and other human activites can release mercury into the atmosphere where it falls to the ground and pollutes soil, water and eventually food in the form of methylmercury – a toxic form of the metal. Some of the highest exposures to this form occur in gold-miners who are exposed through their work and the general population through eating contaminated fish and rice.

Mercury is a well known neurotoxin that affects brain and nervous system development and function at higher exposure levels. The metal is also linked to increased risks of a range of cardiovascular disease, including hardening of the arteries, coronary heart diseases, lung embolism, high blood pressure and vessel obstruction. The mechanism for the relationship has eluded researchers.

In the study, the authors collected blood, isolated the red blood cells, exposed them to low levels of mercury and examined effects in various ways – alone, in blood plasma, in tissue samples and in rats. They determined cell shape differences, measured release of proteins key to clotting and analyzed how well the cells stuck to the inside of vessel walls.

They used relatively low concentrations of mercury – 0.25 to 5 micro molar (uM) - which is within the upper range typically measured in blood of those exposed through contaminated fish consumption.  And found that this caused the red blood cells exposed in culture dishes to change shape and release fragments of their outer cell membrane, results of a process called programmed cell death. The changes are consistent with the process of blood clotting and are a likely way that mercury exacerbates heart disease.

The authors found similar results in rats. The 0.5 – 2.5 milligram per kilogram (mg/kg) doses increased the formation of blood clots and the same protein changes.