Some of the relationships between geochemical environment and health and disease are well documented; for example, deficiency of iodine in soil and water and dysfunction of the thyroid gland—goiter and hypothyroidism in the adult, cretinism in the infant-child, and increased risk of thyroid cancer.

Recent evidence suggests that those relationships we know about are but the tip of the iceberg, and that geochemical environment has a profound influence on the level of health of human beings and other animals; moreover, the geochemical environment, particularly as it affects intake and utilization of trace elements, plays a major causal role in many...