levels at the latter concentration-exposure time combination. In healthy subjects, no lung function measurements were changed at 2.0 ppm for 2 h (Anglen 1981). The FEV₁, a particularly reproducible and sensitive measure of obstructive or restrictive flows in the lung (Witschi and Last 1996), changed by less than 10% following exposure at 1 ppm for 4 h. The atopic individual did not tolerate the 1-ppm exposure during a second 4-h exposure period because of serious respiratory effects.

In the study by D’Alessandro et al. (1996), subjects with a clinical history of asthma were tested. In the study by Shusterman et al. (1998), subjects with seasonal allergic rhinitis were tested. A concentration at 0.4 ppm for 1 h elicited no statistically significant response in airflow or resistance in asthmatic subjects (D’Alessandro et al. 1996). In the same study, a concentration at 1.0 ppm for 1 h elicited significant changes in several pulmonary function parameters for both normal subjects and subjects with asthma, but the mean changes were considered modest by the study authors. However, the R_aw of one subject with asthma more than tripled during the exposure at 1.0 ppm.

All short-term animal studies were conducted at concentrations that produced effects greater than those defined by the AEGL-1.

The studies by Anglen (1981), Rotman et al. (1983), D’Alessandro et al. (1996), and Shusterman et al. (1998) are all relevant to the development of AEGL-1 values. Those studies addressed sensory irritation as well as symptomatic and asymptomatic changes in several pulmonary function parameters. In addition, the studies used a diverse population, including healthy, atopic, and asthmatic subjects. Exercise was incorporated into the protocol of the Rotman et al. (1983) study, simulating conditions of stress. The studies indicate that 0.5 ppm, for 15 min (Shusterman et al. 1998) or for an interrupted 8 h with incorporation of exercise into the protocol (Rotman et al. 1983), is the highest NOAEL consistent with the definition of an AEGL-1 (i.e., a NOAEL for notable discomfort and irritation accompanied by non-disabling, transient, asymptomatic effects). The next highest concentration tested, 1.0 ppm for more than 4 h, resulted in effects, such as shortness of breath and wheezing, greater than those defined by an AEGL-1. The NOAEL of 0.5 ppm was identified from the study of Rotman et al.

Front Matter (R1-R18)

Introduction (1-7)

Roster of the National Advisory Committee for Acute Exposure Guideline Levels for Hazardous Substances (8-10)

Appendix 1: Chlorine: Acute Exposure Guideline Levels (11-76)

Appendix 2: Hydrogen Chloride: Acute Exposure Guideline Levels (77-122)

Appendix 3: Hydrogen Fluoride: Acute Exposure Guideline Levels (123-197)

Appendix 4: Toluene 2,4- and 2,6- Diisocyanate: Acute Exposure Guideline Levels (198-249)

Appendix 5: Uranium Hexafluoride: Acute Exposure Guideline Levels (250-291)