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This teaching guide is designed to complement the 20-minute video, The Truth About H2O. Click here to request the video. Please note that video supplies are limited and may no longer be available.Living UnleadedAnyone who’s ever read a Superman comic book knows about the Man of Steel’s incredible powers, as well as his Achilles’ heel, kryptonite. When his enemies wanted to conceal the deadly green stuff, they hid it in a lead-lined container, since the super hero’s x-ray vision couldn't penetrate the dense metal. The rest of us mere mortals have taken a hint from Clark Kent's alter ego and worn lead "aprons" when getting an x-ray at the dentist's or doctor's office. Lead has several useful applications, including blocking radiation, but if even a small amount gets inside a human body, it can be toxic. And even all of Superman's powers can’t undo the effects of lead ingestion. It is very difficult to remove, and without treatment, it stays in the body for a lifetime. A Little History By digging down nearly 21 feet and studying sediments that have accumulated over the past 14,000 years, the scientists found that people were exposed to lead long before learning to smelt it. Bog waters don’t mix with nearby rivers or underground water and their only source for things like lead is what settles out of the air. The sediments and their contents showed researchers that about 9,000 years ago glaciers that covered Scandinavia moved, revealing the terrain beneath. The ratio of two types of lead in the dust that settled in the swampy waters changed, indicating that its source was the newly uncovered rocks of Scandinavia, finely ground from movement of the sheets of ice. By about 3,000 years ago, the most common types of lead found were those produced by human activities rather than natural rocks and dust. It’s been that way ever since. The good news from the research is that lead levels in the atmosphere are decreasing, thanks to the recent efforts to cut lead emissions from industry and cars. Findings from the bog confirm that we humans have been mining and using the heavy gray metal for about 3,000 years. It was the first metal extracted from its ore, and started mankind on the road of metal technology. Those clever ancient Romans, with their penchant for moving water around via aqueducts, created lead plumbing pipes (a good thing for those communal Roman baths). They worked so well that lead plumbing was used in the United States until just a few years ago, when the dangers of lead poisoning became widely known. Lead also has been a component in pewter, lead crystal glassware, bullets and storage batteries. Lead solder was used at one time to seal food cans. And for many years, until the findings about its toxic effects, lead was in gasoline and paint - substances that exposed many of us unknowingly. Cause and Effect Lead-based interior paint, in common use before being banned in 1978, has been a significant source of lead levels in humans. Again, children are particularly vulnerable. Paint often chips and flakes as it ages, and some children pick at and eat the paint flakes (the term "pica" is used to describe the habit of eating non-food items). Some also chew on window sills and trim that is low enough to reach. Once in the body, lead can affect a number of organs and organ systems. These include: Getting the Lead Out By the 1920s and 1930s, many nations limited the use of lead in interior paints. The U.S. government did not; in fact it wasn’t until the 1960s that the dangers of lead poisoning began to be widely known. The Clean Air Act of 1970 required catalytic converters on cars, which indirectly reduced lead content in the air, and in 1978, residential use of lead-based paint was prohibited. By the mid-1980s, the problem of lead in gasoline was addressed, when the U.S. Environmental Protection Agency ruled that the allowable lead content in gasoline had to be reduced from 1.1 grams per gallon to 0.1. The EPA also wanted a complete ban on the use of lead in gasoline by 1988, but this measure was not passed. Remember the lead water pipes? In 1975, the Safe Drinking Water Act mandated a lead level in drinking water of no more than 15 parts per billion. The act was amended in 1986 to address one cause of lead in water: the use of lead in the installation of any new public water system or the repair of existing water systems was banned. An Ounce of Prevention... There are "hidden" ways lead can come into a home. Some ceramic dishes, especially those made outside the United States, can have lead in the glaze. Lead crystal glassware obviously contains lead, and some cosmetics and ethnic medicines (in Hispanic and Asian communities) made outside the United States are also sources of lead. It was also recently reported that a popular jewelry item, "WWJD" block necklaces, were a possible source of lead contamination. Necklaces made in China, Korea and Taiwan may contain lead, and teens wearing them were putting the blocks in their mouths. To prevent lead contamination from dishes and lead glassware, the
following steps are recommended: You may not be able to eliminate all sources of lead contamination from your home or other environments, but a little research and precaution can certainly cut your risk. And remember the good news from the Swiss bog? Lead levels in the environment are dropping. Superman would be proud. Sources Watering
Camden Yards | Thorton Creek Watershed | Stormwater Management Last Updated: 02/16/03 |
