Cans. Solder in tin cans, usually used to hold the seam together, contains lead; some are nearly 100 percent lead. Some can manufacturers are changing this, but progress is slow. Avoid lead-lined containers or cans whose seams have a shiny, metallic solder appearance. Many imported cans contain lead. The leaded plugs in evaporated milk cans may contaminate the milk.
Cosmetics. Many pigments and other substances used for makeup and other cosmetics contain lead. Historically, lead has been part of face paints and other beauty creams.
Cigarettes. Lead is occasionally a contaminant in cigarettes. Lead arsenate may be used as an insecticide in tobacco growing.
Pesticides. Many pesticides and insecticides contain some lead, mainly as the lead-arsenate base.
Methods of toxicity: Though this is not completely clear, lead most likely interferes with functions performed by essential minerals such as calcium, iron, copper, and zinc. Lead does interrupt several red blood cell enzyme systems, including delta-aminolevulinic dehydratase and ferrochelatase. Especially in brain chemistry, lead may create abnormal function by inactivating important zinc-, copper-, and iron-dependent enzymes. (When body levels of these three minerals are high, there is first less absorption of lead and then more competition with lead for enzyme-binding sites.) Lead affects both the brain and the peripheral nerves. It may also diminish hemoglobin synthesis and can react with cell membranes. This may cause increased permeability of the cells and damage or even death of those cells. Lead can displace calcium in bone, deposit there, and form softer, denser spots that can be seen on X-rays as "lead lines."
Lead also binds with the sulfhydryl bonds and inactivates the cysteine-containing enzymes, thus allowing more internal toxicity from free radicals, chemicals, and other heavy metals.
Lead is also an immunosuppressant; it lowers host resistance to bacteria and viruses, and thus allows an increase in infections. It may also influence our cancer risk. How lead affects the gastrointestinal tract causing symptoms, including a coliclike pain, is still uncertain.
Symptoms of toxicity: An estimated nearly 20 percent of men and 10 percent of women have problems with lead toxicity, though it is not clear what levels of chronic lead toxicity, which is most common, will produce symptoms. Lead in the body subtly interferes with optimum function and general health, and other toxicity factors may affect this. Lead accumulation may also cause shifts in important body minerals, such as zinc, calcium, and manganese.
Early signs of lead toxicity may be overlooked, as they are fairly vague: headache, fatigue, muscle pains, anorexia, constipation, vomiting, pallor, anemia. These can be followed by agitation, irritability, restlessness, memory loss, poor coordination and vertigo, and depression.
Acute lead toxicity symptoms include abdominal pain similar to colic, nausea and vomiting, anemia, muscle weakness, and encephalopathy. Lead encephalopathy is a brain syndrome that can arise also from advanced chronic toxicity. It is characterized by poor balance, confusion, vertigo, hallucinations, and speech and hearing problems.
A low level of lead intoxication may affect brain function and activity more subtly, influencing intelligence, attention span, language, and memory. Insomnia and nightmares may be experienced. Hyperactivity and even retardation and senility may also result. Moderate levels of lead may reduce immune and kidney function and increase risk of infection, and may be another factor in increasing blood pressure. There is some suggestion that lead intoxication may correlate with cancer rates. Further research is needed in this area. With heavy lead intoxication, death may result.