Lead has long been a reliable consumer metal but many years ago we started to learn that it can be harmful to our health. Unfortunately, lead is common to city plumbing, which is how we learned about its health risks in the first place. For example, decades of research and reports has exposed that exposure to lead can lead to behavioral problems and even learning disabilities among children. The latest research, though, shows something far more severe: exposure to lead can result in mental illness.
The study followed 579 people for thirty years—mostly white children in Dunedin, New Zealand—so the data is somewhat limited, but still has the most promising psychiatric follow-up with adults who were exposed to and tested for lead as children. Indeed, this is quite a specific population so we cannot necessarily generalize the findings, but it is definitely a place to start. Actually, Columbia University Medical Center epidemiology professor Pam Factor-Litvak advises that the specifics do not diminish the study’s relevance.
While she was not directly involved with the study, Factor-Litvak notes, “It’s one of the premiere cohort studies in the world. All of the measures in this study, to my knowledge, have been done with extreme thought, and they’ve used state-of-the-art measures.”
Of course, there is something to be said about the commitment behind the study. For one, the Dunedin Multidisciplinary Health and Development Study has been tracking this group of people since they were only three years old. In addition, the team of scientists—most of whom came from Duke University—compiled various assessments to assess the mental health of these subjects. The assessments included data taken from medical records, clinical interviews, and questionnaires from relatives and close friends.
So what did all of this uncover? Well, the level of lead exposure within the cohort ranged from 4 to 50 micrograms per deciliter, with a mean of 11. The United States Centers for Disease Control and Prevention considers just 5 mcg/dL as the actionable level; though they maintain that no level of lead exposure is safe for children.
After considering other variables and factors (including socioeconomic status, family medical history, maternal IQ, etc) the study found that every increase of 5 mcg/dL was associated with a 1.34 point increase in overall psychopathology. The study is ongoing, of course. The subjects were all born between April of 1972 and March of 1973, so this phase uses data collected until the subjects were 38. The next stage of the cohort is beginning and will end when the subjects turn 45.