Lead, an element found in the earth's crust, has been used by humans for thousands of years. Hundreds of useful products—both ancient and modern—have contained lead: products as diverse as pipes, food containers, gasoline, cosmetics and paint.
The story of lead, once it enters the human body, is a less happy one. Millions of humans worldwide have been (and continue to be) poisoned by this mineral. As early as the sixteenth century, reports were kept on poisoned metal workers in Europe. Yet it wasn't until the 1970s, when blood lead levels started being collected in this country on a population-wide basis, that the true extent of contamination was shown. A large government study conducted between 1976 and 1980 highlighted those at greatest risk: poor, urban children under age six. Though African-American children have been disproportionately affected, an astounding 85 percent of preschoolers were exposed to or contaminated by lead back then, using today's stricter definition of a blood lead level of 10mcg/dL or higher.
Numerous studies showed the three biggest sources of lead: leaded gasoline, leaded paint and sealants of canned food. Fortunately, a serious government public health campaign followed. In 1977, regulations reduced the maximum lead content in paint to 0.06 percent by weight, down from as much as 50 percent! The maximum lead content of gasoline is now 0.1g/L, down from approximately 1.5g/L, and the technique of using lead to seal cans has been discontinued. The efforts were successful. By reducing exposure to new sources, the United States has seen a 90 percent decline in lead-poisoned children over the past 20 years.
This sounds, and is, terrific, but sobering problems remain. The lead already contaminating our environment decays naturally over millions of years, so existing lead continues to pose a serious risk. Also, there are other, harder to control sources of lead that, while more of a problem in other countries, come into the Inited States as well: ceramics glazed with leaded glazes (often from Mexico), some non-Western cosmetics, some Ayurvedic medicines, emissions from metal refineries and battery-recycling plants, even some toys and crayons imported from China. Finally, though the number is much lower today, there are still over one million children in this country estimated to have unacceptably high blood lead levels. And though our current cut-off defining a high lead level is 10mcg/dL, newer studies are showing very subtle loss in IQ at lower and lower levels. Basically, there is no 'safe' lead level.
The Effects of Lead
So how does lead get into our bodies and what does it do once it gets there? Though fine particles of lead suspended in dusty air can enter the body through the lungs, most of the lead enters children's bodies through the gut, after having been eaten as small chips or contaminated dust or dirt. Small leaded particles of chipped paint, particularly around friction spots like window sills and doors, settle down and become part of household dust. Likewise, an external renovation involving scraping off old paint contaminates the dirt around the perimeter of the house. Infants who chew on surfaces are at particular risk, as are toddlers whose mobility, curiosity and hand-to-mouth behaviors can lead to lead ingestion.