In reply
We appreciate the insight offered by Dr Grant and agree that the health impacts of polycyclic aromatic hydrocarbons (PAHs) and ambient elemental carbon (of which black carbon is a surrogate measure) are an important area of current and future public health research, particularly research concerning cognitive aging.
Emerging findings have implicated exposure to PAHs, particularly benzo[a]pryrene, as a potential deleterious influence on children's cognitive and behavioral development.1 To our knowledge, no study has evaluated exposure to PAHs in relation to cognitive outcomes in adulthood, but an adverse link is plausible, supported in part by accumulating evidence that exposure to tobacco smoke is associated with cognitive decline and dementia.2-4