Over the last 20 or so years of my career in epidemiology, I have been involved in a wide variety of other research areas. These include:
Investigation of the Cancer-Causing Effects of Low Levels of Arsenic in Drinking Water
My doctoral research was an investigation of whether or not low levels of inorganic arsenic in drinking water caused internal cancers, particularly cancers of the bladder or lung. This work produced some of the earliest scientific publications in what later became a major environmental epidemiology research area, particularly when it was found that tens of millions of people in some areas of the world, such as Bangladesh and West Bengal, were exposed to high levels of arsenic in their water supplies. The arsenic generally came from natural geologic sources and could be difficult to remove from water supplies.
- Bates, M.N., Smith, A.H. & Hopenhayn-Rich, C. Arsenic ingestion and internal cancers: A review. Amer J Epidemiol. 1992;135:462-476.
- Bates, M.N., Smith, A.H. & Cantor, K.P. Case-control study of bladder cancer and arsenic in U.S. drinking water supplies. Amer J Epidemiol. 1995;141:523-530.
- Bates MN, Rey OA, Biggs ML, Hopenhayn C, Moore LE, Kalman D, Steinmaus C, Smith AH. Case-control study of bladder cancer and exposure to arsenic in Argentina. Amer J Epidemiol 2004; 159:381-9.
Investigation of Cancer Risks in Firefighters
It has long been a matter of debate whether firefighters are at increased risk of cancer. Most epidemiology studies have examined mortality in firefighters, an outcome which is insensitive to cancer types that are infrequently fatal. I carried out two epidemiology studies of cancer in firefighters—in New Zealand and in California—which examined incident cancers. Both of these studies showed the strongest cancer association was with testicular cancer, a cancer which now has a high cure rate, provided it is treated early. One other large study from Florida has confirmed this finding. Although we do not know why firefighting might be a risk factor for testicular cancer, the International Agency for Research on Cancer (IARC) has recently classified occupational exposure as a firefighter as “possibly carcinogenic to humans” (Group 2B). The strongest epidemiologic evidence for such an effect was for testicular cancer.
- Bates, M.N. Lane, L. Testicular cancer in firefighters: A cluster investigation. NZ Med J, 1995; 108: 334-7.
- Bates MN, Fawcett J, Garrett N, Arnold R, Pearce N, Woodward A. Is testicular cancer an occupational disease of fire fighters? Amer J Indust Med 2001, 40:263-70.
- Bates MN. Registry-Based Case-Control Study Of Cancer In California Firefighters. Am J Indust Med 2007; 50:339-344.
Possible Health Effects of Dental Amalgam Fillings
Dental amalgam fillings, containing nearly 50% mercury, are widely used in the world, although use has markedly reduced in some countries. Although amalgam fillings have been used by dentists since the early part of the 19th Century and are known to “leak” very small amounts of mercury during chewing, teeth grinding (bruxism) and drinking hot liquids, their safety has been little investigated. I was principal investigator of the largest epidemiology study that has been conducted to date of this issue—using a cohort of 20,000 New Zealand military personnel. Results of this study were generally reassuring, showing no association with either kidney disease or chronic fatigue syndrome, both of which had been hypothesized as associated with amalgam fillings. However, it also highlighted the need for further investigations of this issue, particularly for diseases more common in the elderly, such as Alzheimer’s and Parkinson’s diseases.
- Bates MN, Fawcett J, Garrett N, Cutress T, Kjellstrom T. Health effects of dental amalgam exposure: a retrospective cohort study. Int J Epidemiol 2004, 33: 894-901.
- Bates MN. Mercury amalgam dental fillings: an epidemiologic assessment. Int J Hygiene Env Health 2006; 209:309-316.
- Bates MN. Dental amalgam fillings: a source of mercury exposure. In: Nriagu JO (ed.) Encyclopedia of Environmental Health, volume 2, 2011; pp. 11–20 Burlington: Elsevier.
Exposure to Organochlorine Compounds
Probably all people on the planet contain some amounts of the persistent and bioaccumulative compounds—organochlorine pesticides and their metabolites (e.g., DDT, DDE, dieldrin), PCBs (polychlorinated biphenyls), and polychlorinated dibenzo-p-dioxins and furans (“dioxins”). I was principal investigator of several studies that characterized the concentrations of these chemicals in the serum and breast milk of the New Zealand population. This included the first study to obtain a representative picture of the distributions of these compounds in the serum of a national population.
- Bates MN, Thomson B, Garrett N. Reductions in organochlorine levels in the milk of New Zealand women. Arch Environ Health 2002; 57: 591-597
- Bates MN, Selevan SG, Ellerbee SM, Gartner LM. Reporting needs for studies of environmental chemicals in human milk. J Toxicol Environ Health Part A 2002; 65:1867-79.
- Bates MN, Buckland SJ, Garrett N, Ellis H, Needham LL, Patterson Jr DG, Turner WE, Russell DG. Persistent organochlorines in the serum of the non-occupationally exposed New Zealand population. Chemosphere 2004; 54:1431-1443.