Health Consequences Can Be More Severe When Multiple Environmental Toxicant Exposures Occur at the Same Time!

 

     When people are exposed to environmental toxicants, heath experts can not always predict the level of biological response. In other blogs, I discuss this and attribute it to the fact that every exposure is different in scope and intensity. In addition, every individual will react differently for a variety of reasons that include other environmental factors, overall health status and genetics. This is also true of multiple exposures at the same time or close together in time. With this in mind, scientists and health professionals must assess levels of all exposure to determine health consequences. Unfortunately, the health impacts of multiple exposures can be greater than the health impacts of exposures alone.  Beier et al has demonstrated this to be the case in their new study.
      Other studies have shown that "lead exposure and obesity are co-occurring risk factors for decreased bone mass, especially in low socioeconomic communities. In the Beier study, mice were exposed to a high-fat or low-fat diet. In addition, the mice were exposed to a lifetime of lead (Pb) in their drinking water. The results of the study showed the high-fat diet mice had increased body mass and glucose intolerance. Both the high-fat and lead increased fasting glucose and leptin. Both Pb and high-fat had reduced bone quality and the PB and high-fat together had a worse effect on thesame parameter. Mechanical bone properties of strength were depressed in Pb-exposed bone but was unaffected by a high-fat diet. Both agents promoted osteoclastogenesis and adipogenesis and decreased osteoblostogenesis. Combining Pb and fatty acids combined enhanced the effects of PPAR-y and  inhibited B-catenin.  The author noted that when studying toxicants, 'one must assess them together with other risk factors relevant to human health.'"
      Taking this into account, let us review another study that I mentioned earlier. In that study, it was shown that increased hypermethylation and a decrease in the expression of IFN-Y and regulator T cells occurred when the two toxicants, second-hand smoke and ambient air pollution,were combined. Generally, the decrease on the expression of the T cells and IFN-y was less severe when the exposures happened alone.


Effects of Combined Exposure to Lead and High-Fat Diet on Bone Quality in Juvenile Male Mice. Environmental health perspectives (10 April 2015) by Eric E. Beier, Jason A. Inzana, Tzong-Jen J. Sheu, et al. http://www.citeulike.org/user/kimberlykramer2015/article/13580466

Secondhand smoke in combination with ambient air pollution exposure is associated with increasedx CpG methylation and decreased expression of IFN-γ in T effector cells and Foxp3 in T regulatory cells in children. Clinical epigenetics, Vol. 4, No. 1. (2012), doi:10.1186/1868-7083-4-17 by Arunima Kohli, Marco A. Garcia, Rachel L. Miller, et al.  http://www.citeulike.org/user/kimberlykramer2015/article/13578755