As noted repeatedly in prior posts, toxic torts require proof of causation. As such, an assessment of alternative explanations for the disease or illness at issue becomes important.
The consumption of alcohol (usually in excess of some amount) has been associated with ovarian and breast cancer in women, and cancers of the mouth, esophagus, pharynx and larynx, colon-rectum, liver, and stomach in both genders. (See for example http://en.wikipedia.org/wiki/Alcohol_and_cancer.) Researchers report, based on studies of significantly large groupings of individuals, that if one assumes causation [a not insignificant assumption, though one based on some good medical evidence], then drinking more than a pint of beer a day can substantially increase the risk of some cancers. The Europe-wide study of 363,988 individuals found one in 10 of all cancers in men and one in 33 in women were caused by past or current alcohol intake. More than 18% of alcohol-related cancers in men and about 4% in women were linked to excessive drinking.
Thus, in cases involving allegations of (say) exposure to "toxic chemicals" and an allegedly resultant cancer of the type above noted, counsel should review the past and current drinking habits of the complainant to ascertain the extent to which the alleged harm may be due to excessive drinking (which, per the study, is not what most individuals think of as excessive).
A twist on this risk, of course, is whether those selling alcoholic beverages have an obligation to disclose this potential adverse impact from consumption of alcohol-containing beverages. cf. Matrixx Initiatives, Inc. v. Siracusano, 131 S. Ct. 1309 (2011).
The study can be found at http://www.bmj.com/content/342/bmj.d1584.