Epidemiology is the study of the factors, frequency, mode of transmission, evolution and implementation of ways to prevent disease.  

In analytic epidemiology – the research and studies involving risk and protector factors of disease – specific hypotheses about the incidence, distribution and control are investigated through collection and analysis of biological markers.

With more than 25 years of collaborative research experience in the analysis of blood, urine and toenail clippings, scientists at MURR have made possible a greater understanding of the role of essential trace elements (e.g., iodine; selenium) and potentially toxic trace elements (e.g., arsenic; mercury) on human health and the environment.

As an example, in 2007 over 3,000 toenail clippings were analyzed at MURR to investigate the suppositions relating dietary trace-element nutrients and exposure to toxic elements to the incidence and progression of chronic diseases such as cancer, coronary heart disease and diabetes.

The selenium concentration found in toenail clippings reflects geographical differences, and is affected by cigarette smoking, supplement use, gender and age. The incorporation of this element in finger and toenails joins together approximately 3-6 months of dietary intake proportional to nail length.  This nail monitor has been used successfully to demonstrate the inverse relationship between selenium status and predicted cancer mortality in men and women.  Selenium has in case-control studies shown a protective effect against prostate and bladder cancer.

• Neutron Activation Analysis (NAA) of fluoride in toenail parings has been used to study fluoride hypothesis in osteoporosis. 
  
  
• Epiboron NAA has been used to analyze toenail specimens for ¹⁷iodine – to study thyroid cancer risk factors.
  
  
• Chromium status at baseline, as measured by the toenail biomonitor using NAA, has been found to be lower in diabetics and lower still in diabetics with heart disease, compared to healthy controls. 
  
  
• Further utilizing the toenail biomonitor, the theory that even relatively low-levels of arsenic in drinking water increase the risk of non-melanoma skin, lung and/or bladder cancer is being studied. 
  
  
• The influence of glutathione S-transferase M1 (GSTM1) on methylation of inorganic arsenic in drinking water and potential change in the toenail biomonitor for arsenic has been studied in a small New Hampshire population. 
  
  
• Stable-isotope Ca-46 and Ca-48 measurements on the effect of vitamin D and calcium on percent-true calcium absorption in children with juvenile rheumatoid arthritis are also being investigated.