Samantha Berg

In 1959 a study in California started freezing the blood of 20,000 pregnant women, and half a century later that freezer answered the question everyone is still arguing about: what DDT did to people. DDT was never hidden from you. It was the opposite. In June 1947 Pennsalt ran a full-page advert in Time with a chorus line of a housewife, an apple, a cow, a potato and a dog all singing DDT is good for me-e-e. You could buy it as wallpaper for the nursery, ready pasted, just dip in water and hang. You could buy a lampshade soaked in it, so the heat of the bulb spread it invisibly round the room. The adverts said to comb it through a child's hair for lice. The trucks fogged the streets and the children ran in the cloud. The man who found what it did to insects got a Nobel Prize in 1948. The line was that it was harmless to warm-blooded animals, and it was repeated with total confidence for 25 years. Plenty of people are still repeating it. In Oakland, from 1959 to 1967, the Child Health and Development Studies enrolled about 20,000 pregnant women, drew their blood, and put it in a freezer. Then it waited. It followed the babies, who grew up in the peak years of American DDT use, and it followed their babies. In 2015 the daughters were in their fifties, and 118 of them had breast cancer. The researchers went back to the freezer and measured the DDT in their mothers' blood from the week they were born. The daughters whose mothers carried the most were 3.7 times more likely to have the disease than those whose mothers carried the least. The thing was in them before they drew breath. In 2021 they went down another generation. 365 granddaughters, born long after the ban. The ones whose grandmothers carried the most DDT in pregnancy were fatter and had started their periods younger, both of which raise the risk of the cancer their mothers got. Half of the eggs that became those granddaughters were already inside the grandmother when the fog came down the street. A pregnant woman is three generations at once. Her, the baby, and the eggs in the baby. The spray truck got all three in one pass. Harmless to warm-blooded animals. The warm-blooded animals took 54 years to answer, and the answer is in a freezer in California with a name on every tube.