In this bumper issue we carry an important debate about the persistent organic pollutants and their health effects. Writing this at the end of summer, I’m struck by the fact that this year I have seen sparrows twice. Once in the Yorkshire Dales and once on Martha’s Vineyard. I can’t remember the last time I saw sparrows in Manchester or Liverpool. In Rachel Carson’s book Silent Spring, which was published in the early 1960s, one chapter is called “Where no bird sings”. Forty years later our set of papers pick up the real and continuing impact of what Rachel Carson’s talking about. The persistence of organic pollutants in our environment, their ability to travel long distances, to turn up in polar regions and extreme bits of the food chain, have consequences for human and animal health, which we …