Introduction - the brain's new chemical plaques mimic ageing; neurobehavioural effects and exposure epidemiology; methods for measuring neurobehavioural function and for deriving prediction equations for tests in people unexposed versus those exposed to chemicals; chemically exposed patients; hydrogen sulphide exposure from refineries in cities; chlorine and cresylate from a train derailment; adverse effects from hydrogen chloride; effects of airborne arsenic at Bryan-College station, Texas; neurobehavioural effects of residential chlordane; visual and neurobehavioural impairment associated with polychlorinated byphenyls (PCBs); exposures to chemical mixtures rich in trochloroethylene - residential and occupational; combustion - toluene rich vapour exposure; aluminium recycling vinyl chloride and other contaminants; diesel exhaust; mechanisms of brain damage from chemicals; prognosis and treatment; future of neurotoxicology; protecting brains worldwide strategies.