A new study into tungsten exposure in drinking water has found that tungsten accumulates in porous tissue near to the end of bones[i]. These findings could cast doubt over the once-universal assumption that tungsten poses little or no health risk to the general human population[ii].
Tungsten has the highest melting point of any metal and has remarkably high density and hardness, making it an excellent choice of material for applications such as cutting tools, ammunition and medical devices. It is also used in catalysts and super alloys.
Many regulatory agencies have set limits on exposure to airborne tungsten dust, to protect workers who mine and process the material. However, there are very few officially mandated limits on water-soluble tungsten compounds, to which a broader range of people are exposed. The World Health Organisation does not regulate tungsten compounds in water.
In the early 2000’s, a link between a cluster of childhood leukaemia cases in Nevada and high levels of tungsten in drinking water supplies was investigated[iii] [iv]. The United States Centers for Disease Control and Prevention suggested that the toxicology and carcinogenesis of tungsten should be studied. Research thus far has produced mixed results. Some studies have found that other areas with higher levels of tungsten in drinking water did not have a higher-than-normal incidence of cancer. Elsewhere studies have found that tungsten seems to augment the toxicity of cobalt, in subjects who are exposed to both metals. Mixed findings have warranted further studies which show how tungsten accumulates in the body.
The latest study, in mice, found that tungsten accumulated in test subjects’ bones, but did not do so in a uniform pattern. Rather, it was concentrated in certain areas, specifically in bone marrow and porous bone tissue. This suggests that tungsten is incorporated into the bone during growth and remodeling, which may mean that young, growing individuals are particularly susceptible to tungsten-related health risks. What is more, tungsten in bone was found in a different chemical form to the administered form. The study therefore confirms that tungsten is chemically active in the body. The study also found that tungsten in the outer layer of bone, the cortex, was retained even after the mice were given tungsten-free water for eight weeks.
Koren Mann, co-author of the study, said:
‘We believe that many of the biological effects of tungsten we’ve been investigating will be traced back to changes in the bone’, and, ‘This includes the effects on the immune system, stem cells, and cancer’.
These findings are essential to understanding the effects of tungsten on biological processes.
[i] VanderSchee, C. R. et al. Accumulation of persistent tungsten in bone as in situ generated polytungstate. Communications Chemistry 1, 8 (2018). https://www.nature.com/articles/s42004-017-0007-6 (Accessed 18 April 2018)
[ii] Safety concerns over tungsten. Science Daily. 17 April 2018 https://www.sciencedaily.com/releases/2018/04/180417115651.htm (Accessed 18 April 2018)
[iii] Cross-Sectional Exposure Assessment of Environmental Contaminants in Churchill County, Nevada. Centres for Disease Control and Prevention. 6 February 2003. https://www.cdc.gov/nceh/clusters/Fallon/study.htm#complete (Accessed 18 April 2018)
[iv] Rubin, C. S. et al. Investigating Childhood Leukemia in Churchill County, Nevada. Environ Health Perspect 115, 151–157 (2007). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1797848/ (Accessed 18 April 2018)