The study of how substances alter gene expression is part of the field of epigenetics. Some chemical exposures appear to turn on and turn off genes in ways that disregulate cell growth and predispose for cancer. From this perspective, our genes are less the command-and-control masters of our cells and more like the keys of piano, with the environment as the hands of the pianist.

The study of how substances alter gene expression is part of the field of epigenetics. Some chemical exposures appear to turn on and turn off genes in ways that disregulate cell growth and predispose for cancer. From this perspective, our genes are less the command-and-control masters of our cells and more like the keys of piano, with the environment as the hands of the pianist.

As currently written, the laws require certain manufacturers and users of such chemicals to report any and all environmental releases-either accidental or routine-to air, water, or soil. The Toxics Release Inventory is the main registry of such events, and it is available to the public through the Environmental Protection Agency. It is hardly comprehensive. Toxic emissions reported to the federal government are thought to account for only 5 percent of all chemical releases.

In the world outside this glass room, songbirds are feeding and resting in the trees. Some will take off tonight and not land until they reach Venezuela. Sandpipers, plovers, and broad-winged hawks have already left for Patagonia and Panama. Bats are headed for caves in Kentucky and Tennessee. Out in the Atlantic, humpback whales pass by on their way to the Caribbean. Even now, Canada geese are honking toward us from Quebec. It is a good day for the beginnings of journeys.Every time I look at you, I think, Now I cannot die.

We can change our thinking. Rather than viewing the chemical adulteration of our environment and our bodies as the inevitable practice of convenience and progress, we can decide that cancer is inconvenient and toxic pollution archaic and primitive. We can start seeing the creation of carcinogens as the result of outmoded technologies. We can demand green engineering and green chemistry. We can let our systems of industry and agriculture know that they are suffering from a design flaw.

Between the late 1950s and the late 1980s, more than 750 million tons of chemical wastes were discarded.

I'm beginning to perceive motherhood as a long, slow letting go, of which birth is just the first step.