Dental amalgam, an alloy of about 50 percent elemental mercury, was first introduced in France in the early 19th century. Chosen for its cost-effective durability, this amalgam is a source of very low-level exposure to mercury vapour and generates an enormous amount of controversy. Although the vast majority of patients with amalgam fillings are exposed to levels too low to pose a risk to health, many patients (i.e., those in the upper 99.9 percentile) exhibit urine test results that are comparable to the maximum allowable legal limits for long-term workplace (occupational) safety. Nonetheless, in the United States the National Institutes of Health has stated that amalgam fillings pose no personal health risk, and that replacement by non-amalgam fillings is not indicated. In Norway, amalgam fillings are banned due to concerns over public health and environmental pollution.
In 2002, Maths Berlin, Professor Emeritus of Environmental Medicine and chair of the 1991 World Health Organization Task Group on Environmental Health Criteria for Inorganic Mercury, published[medical citation needed] an overview and assessment of the scientific literature published between November 1997 and 2002 as part of a special investigation for the Swedish Government on amalgam-related health issues. The report concluded: "With reference to the fact that mercury is a multipotent toxin with effects on several levels of the biochemical dynamics of the cell, amalgam must be considered to be an unsuitable material for dental restoration."