Discuss two factors the nurse may assess for that influence the total effect of the exposure?

Paper details:

Environmental exposure and health risk
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Woodruff, T. J., Burke, T. A., & Zeise, L. (2011). The need for better public health decisions on chemicals released into our environment. Health Affairs, 30 (5) 957-965.
The harmful effects of exposure to an environmental toxin can vary dramatically from person to person. Discuss two factors the nurse may assess for that influence the total effect of the exposure?