I've been sort of a harbinger of doom and gloom in the last couple of weeks with this polluted-children report, so I just want to point out one good piece of news in the report, which bears directly on your question.
Two of the substances we tested for in children were PCBs and DDT. These are both substances that have been banned in Canada for quite a few years now--in the case of PCBs, I believe it was in 1977, so going on 30 years. What we found was a good news, bad news story.
The good news is that the levels of these things in kids were measurably lower than in adults. The bad news is that, 30 years after these substances were banned, they're still in kids. So this kind of measurement can be valuable to point out successes, and frankly, in this case it also points out the need for timely action, that even when decisions are made today, these substances are so persistent that it takes decades before they're flushed out of ecosystems and our bodies. But if you look closely at our report, you do see these differences in levels of substances, those banned and those still in use.