Cricular 162—Mercury in New Mexico surface waters

By L. A. Brandvold, 1978, 16 pp., 1 table, 3 figs., appendix, 1 sheet.

Discusses analyses of mercury content in selected surface waters and well samples taken over a 41/2-year period in New Mexico. A total of 151 samples were analyzed by flameless atomic absorption. Mercury poisoning in humans has been known since ancient times. Although some mercury compounds are used medicinally, certain other forms of mercury can be fatal. Mercury vapors are toxic, and the methyl and ethyl mercury compounds used in seed dressings are even more toxic. Until recently, inorganic mercury was not considered a health problem, because it is readily excreted in the urine and not absorbed by the body in large amounts.

Mercury poisonings in Japan completely changed the concepts about inorganic mercury. Since the early 1950s over 100 people have died or have been permanently disabled after eating mercury-contaminated fish from Minamata Bay, Japan. A substantial amount of time elapsed before it was established that the organic compound methyl mercury was the causative agent. Methyl mercury was known to be toxic, but no discharges of this form of mercury had been made to Minamata Bay. The methyl mercury was eventually traced to an industrial discharge containing 20 ppb inorganic mercury. The inorganic mercury was rapidly converted by microorganisms to methyl mercury. The methyl mercury was taken up by small fish and was concentrated up the food chain. The large fish were eaten by the people of Minamata, an action that resulted in death and disability.

This situation did not create any immediate awareness in the U.S. or Canada of the potential for similar crises on this continent. It wasn't until late 1969 that fish in the Saskatchewan River were analyzed and found to contain up to 10 ppm mercury. Commercial fishing was immediately banned in the river. Subsequent analyses showed that fish from Cedar Lake, Lake Winnipeg, Lake St. Clair, parts of Lake Erie, Lake Huron, Lake Ontario, and from most of the St. Lawrence River were contaminated with mercury. Both private and commercial fishing was prohibited in most of these areas. Further investigation traced the source of mercury to chlor-alkali plants utilizing mercury cells and to mercury slimicides used in the pulp and paper industry. These industries are now regulated by very strict effluent regulations, and the pulp and paper industries have discontinued use of mercury slimicides.