The latest mantra from lead poisoning advocates is that “no level of lead in the blood is safe” and that even small amounts of lead can cause “irreversible, lifetime damage.” These statements, however, are disputed by some scientists, including those at the American Council on Science and Health.
After lead was removed from gasoline about four decades ago, the blood lead levels of Americans plummeted so much that no symptoms of poisoning were visible. The question then became: Do low levels of lead cause hidden damage?
Researchers could find no physical effects but some did claim to find behavioral and mental effects, including reduced IQs, shortened attention spans, delayed language proficiency, and “anti-social” behavior. According to the University of Pittsburgh’s Herbert Needleman, “Lead is a brain poison that…increases a child’s risk for doing bad things.” (Needleman was investigated for falsifying his statistics and never exonerated.)
The problem with these findings is that almost all children who get elevated but low levels of lead come from low-income, minority neighborhoods. Many factors in their background besides lead could be causing the negative effects. Researchers try to control these socioeconomic background effects, in order to isolate lead as the sole cause, but it is very difficult to control all of these other factors at once. So research cannot tell for sure if lead is really the cause of the claimed behavioral and mental effects.
One suspicious finding is that all of these alleged behavioral and mental effects are claimed to be irreversible and last a lifetime. That is strange because all of the physical effects – convulsions, fatigue, nausea, irritability, insomnia, constipation, diarrhea, vomiting, poor appetite, anemia, weight loss, among other effects – go away when the lead exposure is stopped and lead levels decline.
If the alleged low-level effects of lead are permanent even when lead levels are reduced substantially, it is entirely plausible that the cause of the effects is not the lead, but some other factor that is also permanent – such as person’s socioeconomic situation.
For example, one research study claims that 65% to 90% of all violent crime in the United States results from childhood exposure to lead. But it is also true that a very high percentage of prison inmates come from low-income, minority neighborhoods. Since the children in these neighborhoods are known to have higher lead levels, any researcher could easily find a correlation between lead and violent crime.
But correlation is not causation. Correlation just means the two factors are found to occur together. Some other factor – like socioeconomic situation – could be causing both factors to occur. Good scientists always take such possibilities into account. Many lead researchers do not. They are advocates with an agenda.