Introduction

1.1 Purpose

In 1977, the National Institute for Occupational Safety and Health (NIOSH) reviewed the available health effects data on occupational exposure to asphalt and asphalt fumes. NIOSH determined that the principal adverse health effects were irritation of the serous membranes of the conjunctivae and the mucous membranes of the respiratory tract [NIOSH 1977a]. Evidence from animal studies indicated that asphalt left on the skin for long periods of time could result in local carcinomas, but no comparable reports of such effects had been reported for humans exposed to asphalt or asphalt fumes. At that time, NIOSH recommended that occupational exposure to asphalt fumes be controlled so that employees were not exposed to airborne particulates at a concentration greater than 5 milligrams per cubic meter of air (5 mg/m³) determined during any 15-min period.¹ Since then, additional data from studies on both animals and humans exposed to asphalt, paving and roofing asphalt fume condensates, and asphalt-based paints have become available. This report provides a review and evaluation of these new data, as well as other information. It is expected that this report will serve as a basis for identifying future research needs.

1.2 Scope

The information in this document assesses the health hazards associated with occupational exposure to asphalt. Chapter 2 presents information about the uses of asphalt and the number of workers potentially exposed to asphalt during paving and roofing operations and during the manufacturing of asphalt roofing products. Chapter 3 describes the chemical and physical properties of asphalt, production methods, similarities and differences between paving and roofing asphalts and asphalt-based paints, and the representativeness of field- and laboratory-generated asphalt fumes. Chapter 4 discusses exposure monitoring methods, extent of worker exposure, and estimates of biological responses in asphalt-exposed workers. Subsequent chapters describe the effects of exposure to asphalt and asphalt fumes on humans and animals, conclusions, recommendations, and needed research.

¹When large amounts of dust are present in the work environment, use of the gravimetric method may lead to erroneously high estimates for asphalt fumes. Where resolution of such problems becomes necessary, a more specific procedure involving solvent extraction and gravimetric analysis should be employed for the determination of asphalt fumes [NIOSH 1977a].