Basis for a particle size-selective TLV for sulfuric acid aerosols

Abstract

The occupational exposure limit for sulfuric acid (H₂SO₄) aerosol in the U.S. and elsewhere is 1 mg/m³, with no restrictions as to droplet size. A review of the literature shows that there are two different responses to inhaled H₂SO₄ which need to be considered in the selection of a Threshold Limit Value (TLV) or other occupational exposure limit. One is a reflex bronchoconstriction caused by the deposition of droplets in the larger lung airways. This bronchoconstriction is of greater magnitude and may cause concern in persons with asthma. The other is the development and progression of chronic bronchitis caused by repeated daily exposures to droplets depositing in the central and more distal conductive airways of the lung. Since the target region for both effects is the tracheobronchial tree, a particle size-selective TLV (PSS-TLV) should be expressed in terms of thoracic particulate mass (TPM). Based upon the literature review, the mass concentration limit for H₂SO₄ TPM should be much lower than the current TLV. A TPM-TLV of 100 μg/m³ should protect nearly all workers from adverse effects.