Unlike zinc or iron, say, there's no biological role for lead in the body. It's just a toxin. Your body, however, treats lead like calcium, so it accumulates in places where calcium is stored, like your bones. Because calcium has essential roles in the communication between nerve cells, muscle contraction and hormones, lead can interfere with these processes.
- Cardiovascular system: high blood pressure, enlarged heart, electrical conduction problems
- Digestive system: pain, constipation or diarrhea, lack of appetite
- Nervous system: headaches, moodiness, irritability, fatigue, memory loss
- Renal system: kidney failure, increased urea levels in the blood, anemia
- Reproductive system: decreased sexual drive and sterility/infertility in both sexes
- Skeletal system: pain in bone and joints as lead accumulates in these areas
These symptoms will be readily noticed in cases of acute lead poisoning with relatively high blood lead levels. But they may not be noticeable in less acute cases, only surfacing during chronic exposure as the blood lead levels gradually rise.
The predominant effect of lead poisoning in children is on their brain. A child's brain isn't completely "hard-wired" like your home. Instead, as a child's brain develops, new neural circuits form in response to new experiences, learning and memories (neuroscientists call this ability to form new connections plasticity). These circuits involve one or more neurons communicating with others in various parts of the brain by sending and receiving chemical messages called neurotransmitters. The new circuits use the neurotransmitter, glutamate.
Now, because the body doesn't distinguish lead from calcium very well, the lead can interfere with glutamate release from the presynaptic cell and a special receptor in the postsynaptic cell called the NMDA receptor. This interference disrupts the plasticity that's so important in the developing brains of children.
The best treatment for lead poisoning is prevention. The U.S. Centers for Disease Control and Prevention recommends that all children ages 6 and under be tested for lead. If you have potential sources of lead in your house -- peeling lead-based paint or lead pipes -- then you or a professional should try to remove them (by professional cleaning, painting over old paint or removing hazardous material).
If blood lead levels are high, prescription medications like Succimer can reduce blood lead. In extreme cases of lead exposure, such as an industrial accident, then toxic levels of lead can be removed by chelation therapy. In this therapy, a chelating agent such as ethylenediaminetetraacetic acid (EDTA) is infused into the blood stream. The agent binds to the lead. The kidneys then excrete the lead-bound EDTA. Again, this treatment is usually reserved for extreme cases of lead poisoning.
We're not the only bodies negatively affected by lead. Lead enters the environment from contaminated water -- water coming from lead drainage pipes, lead-containing rainwater from air pollution or rainwater that filters through contaminated soil. The contaminated water runs into groundwater and aquatic ecosystems. Lead adversely affects the organisms in the lower parts of the food chain in these aquatic ecosystems, such as plankton (microscopic plants and animals) and mollusks. When these organisms die, they decompose and release their lead back into the environment. When they're eaten by organisms higher in the food chain such as fish, marine mammals, birds and humans, then the lead accumulates in the tissues of these higher organisms, thereby producing more ill effects.
Keep reading for more information on this heavy metal and related stories.