The contaminants that have declined are mostly the chlorinated chemicals that are now regulated under the Stockholm Convention. There's an international treaty now to get rid of things like PCBs and what they used to call the dirty dozen, mostly chlorinated chemicals that had been banned in Canada. The new production of PCBs has been banned in Canada for the last 30 or so years.
PCBs have been on the decline. DDT has been on the decline for similar reasons, and there's a whole list of other ones. Some of the chlorinated pesticides such as chlordane have been on the decline. Some are on the way out. Dioxins have been in decline. But there are others that are holding steady. Mercury is one. Then there are others that are on the rise, and those tend to be the chemicals that replaced others. When we got rid of PCBs and we got rid of certain chlorinated chemicals that were used as flame retardants, we replaced them with other things, such as brominated flame retardants, so there's polybrominated diphenyl ethers and a whole range of other flame retardants that have been used to replace them. Others, such as the perfluorinated acids, are also on the rise. But the chlorinated chemicals that have been banned in Canada and the United States since the 1970s and 1980s have been declining significantly.
Those crossbill deformities that I showed at the outset were linked to PCBs and hexachlorobenzene. We don't see those deformities anymore.