Predicting elemental toxicity based on perturbations to natural concentrations Advisor: Sarah Jane White

Investigate how the toxicity of an element (represented by permissible levels in drinking water) is related to the natural concentration of that element (represented by average concentration in world streams) Investigate why this relationship exists through means of toxicology and biological processes, perhaps even evolution Several elements whose environmental behavior and human health impacts are unknown are increasingly being used in emerging technologies; can this relationship help predict whether or not they will be detrimental to human health.

Garrels plot

EPA primary standards and treatment techniques protect public health by limiting the levels of contaminants in drinking water. EPA secondary standards relate to problems such as aesthetic effects, cosmetic effects, and technical effects; these standards are unenforceable

EPA Regulation Need to confirm that both variables are independent ( EPA regulations are NOT dependent or derived from natural concentrations) Once a contaminant makes it on the CCL, the EPA must consider three criteria for regulation. Likely to cause an adverse human health effect Known or likely to occur at a level and frequency of concern at public water systems Will regulation present a meaningful opportunity for health risk reduction For chemical contaminants that are also carcinogens, the EPA sets the MCLG at zero if there is evidence that a chemical may cause cancer and there is no dose below which the chemical is considered safe. For chemical contaminants that are non carcinogenic but can cause adverse non-cancer health effects, the MCLG is based off of the reference dose Where the benefits of a new MCL do not justify the costs, the EPA may adjust the MCL for a particular class or group of systems to a level that “maximizes health risk reduction benefits at a cost that is justified by the benefits”. Currently, there have been three CCLs , one draft CCL (for 2015), and three regulatory determinations. From these regulatory determinations, only perchlorate has been identified to meet the SWDA criteria for regulation in drinking water. Nonetheless, no regulation has been finalized thus far

Next Steps/Conclusion Further investigate why this relationship exists (previous papers point to evolution) Extend this idea to other environmental media such as the atmosphere This wonderful opportunity has strengthened my perceived connection between environmental factors and human health and has gratified my affection for science and fostered further impetus of my interest in healthcare

Thank you to Sarah Jane White and the entirety of the Myneni Group!