Diesel Exhaust

Slowness of response, memory loss and disordered sleep in ten railroad workers and in six electricians referred for shortness of breath suggested that diesel exhaust affected the brain. Neurobehavioral and pulmonary testing was done on seven diesel mechanics, three train crewmen and six electricians. The latter were wiring nine substations of a new shopping mall as it was walled and roofed to become a 0.4 km tunnel.

The 16 men performed significantly less well than did reference men for reaction time, balance, blink reflex latency R-1, Culture Fair, peg placement, trail making, verbal and visual recall. Visual fields were abnormal in 13 with bilateral constriction in 11. Nine men including four who had never smoked had small airways obstruction. No confounding factor nor bias accounted for these differences. The severity of neurobehavioral impairment in diesel exposed workers was related to the degree of enclosure and to its duration. Other cohorts should be studied for confirmation.

Diesel mechanics who were being examined for asbestosis, a chronic scarring lung disease, responded slowly to questions and recalled past events poorly so their neurobehavioral functions were tested. Their jobs entailed tuning diesel engines indoors. Recall memory, balance, reaction time, visual fields and other tests were impaired. These observations were novel and surprising. Fortunately there were opportunities to confirm them in diesel train crews and in electricians who were exposed "indoors" to diesel exhaust. When people exposed downwind of a diesel fire also had neurobehavioral impairment the attribution to diesel exhaust was again supported. This raises questions. Are operators of trucks, buses and cars at risk? Are freeways unsafe? No other explanations compete with attributing this toxic encephalopathy to chemicals in diesel exhaust. Two mechanisms are suggested, hydrocarbons and aldehydes. Naphtha, as the white spirits in spray paint used indoors and in jet fuel and gasoline, has well demonstrated toxicity for the brain and formaldehyde is toxic to the brain as is acrolein, the two carbon aldehyde abundant in diesel exhaust.