The Tissue Reaction in the Lungs of Rats after the Inhalation of Coal Dust Containing 2% of Quartz

Belt and King (1945) found that pure coal dust, whether anthracite or bituminous, was of low pathogenicity, producing only minimal fibrosis; but there was some evidence to show that with increased siliceous matter in the coal the pathogenicity also increased. King, Harrison, and Ray (1949) found that when 5 and 10 mg. of quartz were mixed with 95 and 90 mg. of anthracite coal respectively and injected intratracheally into rats larger and more numerous nodules containing more reticulin resulted than were produced by the injections of clean coal (anthracite with very little ash). Ray, King, and Harrison (1951a) showed that when 2 mg. of quartz was given by intratracheal injection to rats there was no fibrotic reaction in the animals' lungs since it was removed to the hilar lymph nodes, where it did cause some fibrosis. Pure anthracite (100 mg.), when introduced into the lungs by the same route, also produced no pulmonary fibrosis, but when 2 mg. quartz was mixed with 98 mg. of pure anthracite coal and injected into the lungs, fibrotic nodules resulted. Ray et al. (1951b) realized the limitation of their experiment in that the intratracheal tech nique did not simulate dust inhalation. Hence, they suggested the repetition of the experiments by a dusting technique. The present work was undertaken to find out whether a small amount of silica mixed with pure anthracite coal would lead to pulmonary fibrosis. Two dusting experiments were set up, the first with a light exposure to quartz alone and the second with a mixture of 2% quartz and 98% coal.