Responses in the respiratory tract of rats following exposure to sulphuric acid aerosols for 5 or 28 days

Abstract

Sulphuric acid mists have been classified by the International Agency for Research on Cancer as being carcinogenic to humans based on epidemiological findings of respiratory tract tumours. To determine if early changes in the respiratory tract following exposure to sulphuric acid (H(2)SO(4)) aerosols are consistent with the possible development of tumours after extended periods of exposure, groups of female rats were exposed to respirable aerosols of H(2)SO(4) at target concentrations of 0, 0.2, 1.0 or 5.0 mg m(-3) for 6 h per day for either 5 days or for 5 days a week over a 28-day period. Additional groups exposed to 0 or 5.0 mg m(-3) over the 28-day period were retained after exposure for 4 or 8 weeks to assess recovery. Histopathological examinations and quantitative cell proliferation measurements were conducted on the nasal passages, larynx and lung. Achieved concentrations were 0.3, 1.38 and 5.52 mg m(-3) H(2)SO(4). Histological and cell proliferative changes were confined to the larynx and no effects were seen in the nasal passages or lungs. At the two highest concentrations, squamous metaplasia accompanied by significant cell proliferation was apparent after 5 and 28 days of exposure and there was a reduction in the severity of the pathological changes following the recovery periods. No effects were seen at 0.3 mg m(-3) after 5 days of exposure and only minimal metaplastic change was seen after 28 days in a few animals and was not accompanied by cell proliferation. The toxicological relevance of these findings is discussed.

Leukocytoclastic vasculitis associated with sulfuric acid inhalation

“…Chemical agents are widely distributed in a diverse range of products. Sulfuric acid has a wide range of applications and is used in many industries 4 . Our patient used a product called MELT ® to unblock his water drains.…”

Sulphuric acid—the mist created by IARC

“…Histopathological examination was confined to the respiratory tract. Replicative DNA synthesis was measured in the nasal cavity, larynx and lung as an index of cell proliferation (Kilgour et al, 2002).…”

Epithelial Alteration Associated With Recovery From Laryngeal Squamous Metaplasia in Rats: Kinetics of Recovery From a Test Item-Related Change

“…1 As a result, rats are often used in inhalation toxicity studies. The upper respiratory tract, particularly the larynx, is a common target organ for many pharmaceuticals, industrial chemicals, agrichemicals, and environmental pollutants 2 –9 and many regulatory risk assessments for potential inhalation exposure to toxicants are based on lesions observed in the upper respiratory tract of rodents. 10…”

“…4,10 With shorter exposures, regression of squamous metaplasia can occur within 1 week of removal of the inciting stimulus. 6,17…”