Investigation of chronic toxic and carcinogenic effects of gasoline engineexhausts deriving from fuel without and with ferrocene additive

Chronic toxic and carcinogenic effects of gasoline engine exhaust inhalatio n were investigated in rats. The exhaust from the combustion of commercial fuel containing 30 ppm ferrocene additive was compared to exhaust from the same fuel without ferrocene. This study was part of a procedure to get a sp ecial authorization for the use of ferrocene as gasoline additive according to the German Gasoline Lead Act. To generate the exhausts, pairs of engine s of the same type and age were operated on computer-controlled test benche s in a combined urban-freeway driving cycle. The engines were equipped with three-way catalysts and lambda sensors. Rats inhaled the exhausts after di lution at ratios of about 1:20 and 1:40 for 18 h/day, 5 days/wk for 12 mo ( chronic toxicity study) or for 24 mo followed by 6 mo of clean air (carcino genicity study). The limiting factor for the exhaust concentration was the relative humidity of the exposure atmosphere. At defined intervals, body we ight and food consumption, parameters of clinical chemistry, hematology, br onchoalveolar lavage (BAL), and mechanical lung function were measured as w ell as lung clearance and particle retention in the lungs. In the high-dose groups and the controls the complete organ/tissue spectrum was investigate d histopathologically, and in the low-dose groups the respiratory tract. On ly slight exposure-related effects could be detected, like a loss in the ba ckground iron content of the cell pellet of the bronchoalveolar lavage flui d and cytoplasmic inclusions and goblet-cell hyperplasias in the nasal cavi ty. Between the clean-air controls and the exhaust-exposed groups, no expos ure-related differences occurred in body weight development mortality incid ences, or any of the clinical investigations. Ninety-two to 94% of the anim als developed age-related tumors, predominantly in the mammary glands, uter us, adrenals, thyroid, and pituitary. In the respiratory tract a total of f ive tumors was found: one in the controls and four in the low-dose groups. No physical, chemical, or toxicological differences between the exhausts fr om fuel without or with ferrocene were demonstrated.