Evaluating lead exposure and measuring lead levels in humans is not easy. Blood and urine tests are not very good indicators, because lead is cleared fairly rapidly. With acute toxicity, both of these body fluids may have high measurements, but most exposure is chronic. Hair analysis is the simplest and best test for evaluating chronic lead poisoning, which has become much more common with long-term exposure. Hair-test screening for lead is fairly reliable and can be done on both adults and children. Hair (and urine) levels can be remeasured to follow the progress of treatment. Increased body burdens of lead can be shown by testing with an intravenous dose of a chelating drug such as EDTA. A high level of urinary lead elimination suggests increased levels of body stores, especially in the bones. Also, since lead interferes with many red blood cell enzymes such as delta-aminolevulinic acid dehydratase, an increase in delta-aminolevulinic acid in the urine, as well as zinc protoporphyrin and erythrocyte protoporphyrin, suggests problems of lead toxicity. A blood level of zinc protoporphyrin is currently the best way to assess lead toxicity.
Sources: Lead exposure and body lead levels are higher in North America than anywhere else in the world. In the United States alone, it is estimated that approximately 1.3 million tons of lead are used yearly in batteries, solder, pottery, pigments, gasoline, paint, and many other useful substances. Somewhere between 400,000 and 600,000 tons per year go into our atmosphere, onto our earth, into our food, and into our body and tissues. So there is a lot of lead around. The following are some of the common contaminants:
Leaded gasoline. Tetraethyl lead was previously added to all gasoline; it is now used only for older vehicles. After combustion, this lead goes directly into the atmosphere as air pollution and is inhaled by us and other living, breathing entities. It also settles into the earth and its living vegetation; heavily traveled roadways show higher concentrations of lead in the air, soil, and nearby vegetation.
Paint. Though, by law, the amount of lead in paints must be reduced, some still contain lead. Many homes retain lead paints, so this change may not affect us in environmental lead exposure for a couple of decades.
Food. Lead is contained in many foods, especially in those grown near industrial areas or busy cities or roadways. Grains, legumes, commercial and garden fruit, and most meat products pick up some lead. Liver and lunch meats are usually higher. Liverwurst and other sausages may contain more lead than other foods. Roadside vegetation, such as herbs, fruits, and vegetables, has higher concentrations of lead than vegetation growing in more secluded areas. Measurements of lead in trees growing along roads show much more than was present in the 1930s. Bonemeal, a source of calcium and magnesium, is usually made from cattle bones and may contain high amounts of lead. Dolomite, an earth rock source of calcium and magnesium, is usually lower in lead. Pet foods may also be high.
Water. Drinking water may be contaminated with lead. Lead solder in pipes or lead plumbing in older homes and drinking fountains, can leach into the water, especially soft water. A more acid water will also pull lead and other toxic and nontoxic minerals from the piping.
Pottery. "Earthenware" in general has potential for lead exposure. Though some potters refrain from using much lead, it is hard to avoid. When the glazing is inefficient, lead containers can contaminate food stored in them. Fruit juices or acidic foods, such as tomatoes, will tend to pull out more minerals. Glazed coffee mugs should be avoided.