The impact on human health by natural materials such as water, rocks, and minerals has been known for thousands of years but there have been few systematic, multidisciplinary studies on the relationship between geologic materials and processes and human health (the field of study commonly referred to as medical geology). In the past few years, however, there has been a resurgence of interest in medical geology. Geoscientists working with medical researchers and public health scientists have made important contributions to understanding novel exposure pathways and causes of a wide range of environmental health problems such as: exposure to toxic levels of trace essential and non-essential elements such as arsenic and mercury; trace element deficiencies; exposure to natural dusts and to radioactivity; naturally occurring organic compounds in drinking water; volcanic emissions, etc. By linking with biomedical/public health researchers geoscientists are finally taking advantage of this age-old opportunity to help mitigate environmental health problems. The International Medical Geology Association has recently been formed to support this effort.