Recovery from changes in the blood and nasal cavity and/or lungs of rats caused by exposure to methanol‐fueled engine exhaust

Abstract

One group of male, pathogen-free, Fischer 344 rats was exposed to about 17-fold diluted exhaust generated by an M85 methanol-fueled engine (methanol with 15% gasoline) without catalyst for 8 h, and then the rates of recovery from the resulting increased levels of plasma formaldehyde and carboxyhemoglobin in their erythrocytes were measured. The carboxyhemoglobin level in the erythrocytes was restored within 4 h, whereas the plasma formaldehyde level was still elevated after 4 h but was restored to the normal level within 8 h. No methanol or formic acid was detected in the plasma. Another group of rats was exposed to the same dilution of exhaust for 8 h/d for 7 d, and then the recovery from histopathological damage of the nasal cavity and lungs was also examined. Hyperplasia/squamous metaplasia and erosion of the respiratory epithelium lining the nasoturbinate, maxilloturbinate, or nasal septum, and infiltration of neutrophils into the submucosa at level 1 (level of the posterior edge of the upper incisor teeth) were observed immediately after the exposure period. Lesions of the respiratory epithelium at level 2 (incisive papilla) were less than those at level 1. Slight lesions at levels 1 or 2 were still noticed 1 wk after exposure, but not 4 wk after exposure. Just after exposure, decreases of Clara cells in the terminal bronchiolus and of cilia in the bronchial/bronchiolar epithelium were also observed. Moreover, focal hypertrophy of alveolar walls and increase of macrophages were observed in parts adjacent to respiratory bronchiolus. One week after the exposure period, these changes were no longer seen. These results indicate that changes in the blood and in the nasal cavity and lungs caused by methanol-fueled engine exhaust are reversible. However, complete recovery from damage of the nasal cavity caused by 7-d exposure to the exhaust takes 4 wk, and recovery from elevated plasma formaldehyde and erythrocyte carboxyhemoglobin levels caused by a single 8-h exposure takes 4-8 h.

Association between atmospheric ozone levels and damage to human nasal mucosa in Florence, Italy

“…Although squamous metaplasia could be ascribed to other pollutants beside ozone, and although it could indicate potentially irreversible damage, sometimes associated with neoplastic transformation, other studies report that this morphological alteration is associated with repeated exposure to high ozone levels [Cho et al, 1999]. Furthermore, exposure to common air pollutants induces lesions in the nasal epithelium such as squamous metaplasia characterized by progressive recovery in the three-four weeks after exposure [Maejima et al, 1993]. The occurrence of squamous metaplasia in our subjects was not correlated with DNA damage in the nasal mucosa, whereas a significant correlation was found between altered cluster formation and DNA damage.…”

Effect of methanol intoxication on spcific immune functions of albino rats

“…People handling products that contain methanol may inhale the toxic vapor during its evaporation from the product surface. When methanol was proposed for use as an alternate automotive fuel, criticisms were raised that this might result in an unacceptable increase in the risk of exposure to methanol vapors and in the frequency of reported toxic effects (Maejima et al, 1993;CONCAWE, 1995). Apart from the occupational or transportationrelated routes, there are both direct and indirect means by which exposure to methanol can commonly occur.…”

Melatonin improves methanol intoxication‐induced oxidative liver injury in rats

“…It is also ingested as a substitute for ethanol when ethanol is either too expensive or unavailable [1]. When methanol was proposed for use as an alternate automotive fuel, criticisms were raised that this might result in an unacceptable increase in the risk of exposure to methanol vapors and in the frequency of reported toxic effects [2]. Severe metabolic acidosis, and serious clinical disturbances such as blindness, serious neurological sequelae and death can be seen after accidental or suicidal ingestion of methanol [3, 4].…”