Mixed chemical exposures prevent attributing cancers to any single carcinogen

Evidence

Levin had also been searching the scientific literature for studies of TCE. He’d found an epidemiological study of three hundred and thirty dry-cleaning workers, an occupation in which both TCE and perc, the other chemical in the Woburn wells, were commonly used. The study reported significant increases of several different cancers, among them kidney, bladder, and cervix, and also found five leukemia victims where, statistically, only two had been expected. The author of the study considered the leukemia finding only marginally significant, however. And since the workers had been exposed to several chemicals—TCE, perc, and carbon tetrachloride—the study was unable to draw conclusions about the carcinogenic capacity of any single chemical. — , Harr Jonathan - A Civil Action, 673

Categorization

• XREF: Echoes the Woburn wells’ own dual-contaminant problem — the very reason causation broke down in court.
• ADDENDUM: Directly extends ‘Grafting & Growth’-style infrastructure thinking to exposure: shared vectors (dry-cleaning shops, wells) distribute harm across populations who can never prove which thread caused which cancer.