Activist: Medical conditions such as cancer and birth defects have been linked to pollutants in water. Organic pollutants such as dioxins, and inorganic pollutants such as mercury, are ingested by fish and move up the food chain to people, where they accumulate in tissue. Since most cancers and birth defects are incurable, we need to aim at their prevention. Clearly, the only effective way to reduce significantly their overall incidence is to halt industries known to produce these pollutants, given that such industries are unlikely to comply adequately with strict environmental regulations. A flaw in the activist's reasoning is that it ['fails to consider whether industries may voluntarily decrease their output of pollutants', 'takes for granted that certain effects can be produced independently by several different causes', 'fails to consider the possibility that chemicals now classified as pollutants have some beneficial effects not yet discovered', 'fails to consider the possibility that a significant number of occurrences of cancer and birth defects may be caused by preventable factors other than industrial pollutants']