In cases where a person is exposed to more than one threshold contaminant (non carcinogen), it is acceptable to add the HQs calculated from each chemical together if the chemicals have a similar mechanism of action and similar target organ (Health Canada 2004).
In cases where a person is exposed to more than one non-threshold contaminant (carcinogen), it is acceptable to add the ILCRs calculated from each of the chemicals together if the contaminants affect the same target organ and produce the same form of cancer (Health Canada 2004).
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