In its various forms, lead has been used in many everyday products for millennia. The Romans even added it to wine as a sweetener. Its most widespread use, however, was its addition to petrol. And it is this use that has been associated with increased mental health disorders, according to a new study published in the Journal of Child Psychology and Psychiatry.

Americans, especially those born between 1966 and 1986 (largely so-called generation X), have probably suffered from an additional 151 million mental health disorders that would not have occurred without the use of leaded petrol.

The study finds increases in anxiety and depression, attention deficit hyperactivity disorder (ADHD), and neuroticism, as well as decreases in conscientiousness.

Although the toxicity of lead for humans has been known for almost as long as it has been used, the full extent of its effects and the exposure levels at which they manifest is still being uncovered.