The hazards of hazard identification in environmental epidemiology

Table 1 Types of studies based on which the level of convincing evidence of carcinogenicity was reached for a number of exposures^a

Exposure	Type of study
Tobacco smoke	Cohort studies
Diethylstilbestrol	Case-control study (small)
Bis(chloromethyl)ether	Case series
Benzene	Case reports
Arsenic	Ecological study
Several chemotherapeutic drugs	Controlled randomized trials

^aSource: [16]. Evidence rated as convincing when corresponding exactly or closely to category 1 or 2A in the current definitions of IARC [3]

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