Lead

Lead in the ambient air exists primarily as particulate matter in the inhalable size range. The predominant source of atmospheric lead is from motor vehicles and incineration of solid wastes. Trace amounts of lead are still present in "unleaded" gasoline and are emitted in motor vehicle exhaust. Other major sources of atmospheric lead are the extraction and processing of metallic ores.

When atmospheric lead is breathed in, it is absorbed into the bloodstream and distributed throughout the body along with lead from contaminated food and drinking water. Lead accumulation in the body can impair the production of hemoglobin. Clinical lead poisoning occurs when the body's accumulation of lead becomes too high. Symptoms of lead poisoning range from loss of appetite, fatigue, cramps and constipation, and pains in the ankles and wrists to loss of power in the arms and legs, anemia, kidney disease, mental retardation, blindness and death. Lead concentrations in the ambient air are not sufficient to produce lead poisoning but they do increase the risk of harm when other sources of lead are present. And, indirectly, lead fallout from automotive exhaust onto soil and street surfaces can be ingested in considerable amounts by infants and young children.

The current National Ambient Air Quality Standard for lead is a 3-month (calendar quarter) average concentration not to exceed 1.5 micrograms of lead per cubic meter of air.

The current State Standards for lead is a 24-hour average concentration of 1.5 micrograms of lead per cubic meter of air not to be exceeded more than once per year.

Lead was not monitored in Maine during 2007 due to the extremely low concentrations recorded in previous years. The last monitoring occurred in 1993 in Portland and Lewiston . The maximum 24-hour average concentration was .14 micrograms per cubic meter, less than 10 percent of the State standard. The maximum calendar quarter average was .03 micrograms per cubic meter, only 2 percent of the National Ambient Air Quality Standard.