If you live near a known potential source of pollution (i.e. a site that's being examined or remediated) and you have a condition that may be caused or exacerbated by said pollution, you can find info from all sorts of agencies: your local health department, state environmental department, the CDC, the ATSDR, and the EPA. You may find that your town has a local resident advisory board that has meetings you can attend where you can bring up your concerns and get explanations from scientists.
A few caveats:
Unless you have spent your life working in an asbestos mine and you have mesothelioma, a reputable scientist will NOT indicate to you that exposure to a particular site did cause your illness. Why?
1. The links between dangerous chemicals and long-term health effects have generally been quantified only in animal studies (except for a handful of obvious baddies, like lead). And we really don't have the foggiest about healthy adult vs. child or infant exposure. We make educated guesses based on body weight.
2. Potentially synergistic effect of various chemicals in the body (PCE/lead? PCE/benzene/arsenic?) are unknown. We're still working on this "does this 1 chemical cause cancer?" above.
3. Often, folks charge that a single obvious target (a factory, a military base, a dump) caused the problems, but exposure is the cumulative effect of living near busy roads, gas stations, dry cleaners, auto body shops, etc.
4. Cancer is wicked complicated. We know anecdotally that people in polluted areas get cancer at a higher rate (and you need to look at it from a very local neighborhood NOT townwide basis, people!). But to prove this in court is nigh impossible because the same exposures may spawn different cancers in different people.
5. There's a whole world of chemicals that don't have any exposure values. A number of petrochemicals, dyes, and industry byproducts haven't even been looked at.
I'm not minimizing potential harm from contaminants. I'm saying we can't quantify it to the degree that people would like and the degree that a lot of people think we can. The % risk that people publish for exposure at certain sites is based on a huge chain of (conservative!) assumptions.
A lot of people go to public meetings wanting validation that x exposure caused y disease. They often get frustrated when they don't get that validation. It is not a government conspiracy, but the caution of scientists who want to make sure they get things right, enforced by a battalion of lawyers.
Finally, you have to remember that the environmental laws in this country have to pass through a gauntlet of commentary, much of it by big bad industry. Remediation is often done to the letter of the law. If you get all fired up and want to tighten up the law, I'd suggest working through advocacy groups. Your local regulatory representative cannot change national laws and exposure limits. Browbeating said representative may be cathartic but doesn't accomplish anything.