I seem to be reading books in contrasting pairs these days.

One pair is Little Heathens by Mildred Kalish and Horizontal World by Debra Marquart. Both are about growing up on hard-scrabble, midwestern farms, but they couldn’t be more different in tone and style. Kalish finds contentment where Marquart finds burning restlessness. Marquart describes dairy farming as akin to slavery; Kalish’s childhood relationship to cows is downright transcendental. Both have plenty of experience with the cream separator in the milking parlor but use entirely different vocabularies to describe how the apparatus works. Both are wonderful books and manage to find beauty without sentimentality.

Another pair is The Secret History of the War on Cancer by Devra Davis and Toxic Exposures by Phil Brown. These I just reviewed for the Times Literary Supplement. Davis’s book documents the ways in which evidence for environmental links to human cancer have been sidelined, buried, revised away, and discounted. Davis, who is a cancer epidemiologist with a long history in public service within the federal government, is a formidable authority on the topic. She argues that the war on cancer is little more than a cunning re-enactment. Phil Brown’s book looks at the ways that citizen activist groups have struggled to rescue this lost knowledge and create new knowledge about environmental health, albeit contested, with the help of progressive scientists.

My favorite story from Brown’s book is about the ways in which, during the 1960s, the Black Panthers and Young Lords insisted on lead paint abatement in housing even while the industry and government still denied that low-level lead poisoning was a problem for children. By so doing, scientists then had a population of children with declining lead levels and could scientifically demonstrate that, indeed, background lead exposure was harmful to children’s brains. Brown’s book made me realize that the precautionary principle is not just good for public health. It’s also good for science because, when enacted, precaution can provide researchers with unexposed control populations that make demonstrable proof possible.