In most toxic tort cases, the single biggest hurdle for a plaintiff is the problem of causation.
When a personal injury action is brought, the plaintiff has the legal duty of showing that whatever it was the defendant did was the immediate cause of the plaintiff's harm, and that the harm wouldn't have occurred (or been as serious) if the defendant had not acted in the manner that the plaintiff is alleging. As a toxic tort-related example, a plaintiff would need to prove that the toxins in the water caused cancer, and that cancer would not have developed if the toxins hadn't been there.
Health problems that often develop from toxic exposure -- like various types of cancer in the case of asbestos and many chemicals, or like breathing or respiratory problems in the case of many molds -- may not be easy to trace back to one cause. For instance, if you get throat cancer, of course you could argue that it came from drinking contaminated water. Unfortunately, since no one really knows what causes most types of cancer, and since there are often numerous potential causes, the defendant could point out that you don't know that it was the exposure to the toxin that made you sick. This is a problem in many toxic tort cases, with the exception of asbestos cases where a person develops mesothelioma, since that condition develops only as a result of asbestos exposure.
Compounding the problem is the fact that many toxic-tort-related diseases often do not show up for a long period of time after the exposure happened. The more time and distance between the incident and the injury, the harder it is to prove a direct link. It is, naturally, a lot harder to prove that "more likely than not, drinking this water 10 years ago caused my breast cancer today" then it is to prove "he hit me with his car, I broke my leg."
While causation problems are an issue, they do not necessarily disqualify you from bringing toxic tort claims. A few things can help you to get around causation problems including:
In general, the more linking evidence that you can find, the better and more solid your chances of making a successful toxic tort claim.
One of the factors that can help you to get around causation problems -- the high incidence of certain types of illnesses -- also plays another important role in toxic tort litigation. The fact that many people often develop the same or similar problems because of exposure to some toxin can lead to a large number of toxic tort cases being handled as class action lawsuits. Class actions are cases where a group of similarly-harmed plaintiffs all get together in one big lawsuit, instead of everyone filing their own case.
Class actions usually work by first having all of the plaintiffs certified as a class. There is a lead plaintiff who speaks for and makes decisions (with the help of lawyers, etc.) on behalf of all members of the class. This lead plaintiff or group of lead plaintiffs are the ones who go to court regularly, although other class members may be called upon to testify as well. When a class action is settled or when a class action case is won by plaintiffs in court, damages are split among all the members of the class. This is usually done using some formula where people who suffered different levels of harm are given different set amounts of compensation.