In the 1970s, Wald showed that fetal neural tube defects could be detected by measuring alpha-fetoprotein in the pregnant woman's blood.
In 1986 Wald showed that environmental tobacco smoke was a cause of lung cancer[2] and was a member of the US National Academy of Sciences Committee – the first public body that reached this conclusion.
In 2003, with Professor Malcolm Law, he showed that environmental tobacco smoke also causes cardiovascular disease.
In 1991 Wald showed that folic acid supplementation prevented most cases of neural tube defects.
[4][5] He received, in 2000, the Joseph P. Kennedy Jr. Foundation Award,[6] was elected a Fellow of the Royal Society (FRS) in 2004,[7] and knighted in the 2008 Birthday Honours[8] for services to preventive medicine.