Table 8.

Examples of confounding factors that should be considered in epidemiological studies on a possible association between fluoride exposure and intelligence

Residence, particularly urban versus rural areas

Water improvement plants: is fluoride, lead, or arsenic removed from drinking water?

Breastfeeding; breastfed children may have higher IQs

Confounding by other sources of fluoride (e.g., dental products) than drinking water

Background of parents: educational level, socioeconomic status, income, IQ

Birth weight; first-born?

Intake of iodine

Exposure to other chemicals: lead, methylmercury, arsenic, polychlorinated biphenyls