Acute Exposure Guideline Levels for Selected Airborne Chemicals Volume 4 (2004) / Chapter Skim
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Appendix 2: Hydrogen Chloride: Acute Exposure Guideline Levels
Appendix 2: Hydrogen Chloride: Acute Exposure Guideline Levels
Pages 77-122
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From page 77... ...
It is an upper respiratory irritant at relatively low concentrations and may cause damage to the lower respiratory tract at higher concentrations. HCl is very soluble in water, and the aqueous solution is highly corrosive.
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From page 78... ...
That would generate AEGL-2 values that are not supported by the total data set, including data on exercising asthmatic subjects, an especially sensitive subpopulation, because exercise increases HCl uptake and exacerbates irritation; no effects were noted in exercising young adult asthmatic subjects exposed to HCl at 1.S ppm for 45 min (Stevens et al.
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From page 79... ...
Threshold Limit Value (TLV) as a value that will prevent sensory irritation in humans.
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From page 80... ...
The value was then time- scaled to the specified 10- and 30- min and 4-h AEGL exposure periods using the ~ x t = k relationship, where n = 1 based on regression analysis of combined rat and mouse LC50 data (1 min to 100 min) as reported by ten Berge et al.
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From page 81... ...
Experimental Studies Five male and five female adult asthmatic subjects (age 18 to 25 years ty]
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From page 82... ...
2.2.2. Case Reports Reactive airways dysfunction syndrome (RADS)
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From page 83... ...
Other data concerning acute inhalation exposure to HCl in humans are qualitative and dated, making accurate exposure assessment difficult. A summary of those data is presented in Table 2-3.
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From page 84... ...
2.6. Summary No treatment-related effects were observed in exercising, young adult asthmatic subjects exposed to HCl at 0.S ppm or 1 .S ppm for 45 min.
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From page 85... ...
(1974) examined the acute toxicity of HCl vapor or aerosol in groups of 10 male Sprague-Dawley rats exposed to HCl at 41030,000 ppm and groups of 10 male ICR mice exposed to HCl at 2,10057,000 ppm for 5 or 30 min.
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From page 86... ...
Groups of 10 Wistar rats and 15 ICR mice were exposed to various concentrations of HCl vapors for 5 min. HCl concentrations were monitored continuously during exposures via specific ion electrode analysis.
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From page 87... ...
to HCl at 190, ~ 10, 2,780, 11,400, 16,570, or 17,290 ppm for 5 min. HCl exposure concentrations were continuously monitored using a "modified French standard test method." This method is based on continuous titration of the chloride ion with silver nitrate.
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From page 88... ...
HC! exposure concentrations were continuously monitored using a "modified French standard test method." Respiratory rates during exposure were increased approximately 30°/O,50°/O, and 100% for the 500-,5,000-, and 10,000-ppm groups, respectively.
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From page 89... ...
l 993a) , no exposure-related differences in pulmonary function or CO2 challenge response tests were reported 6 or 12 mo post-exposure, with the exceptions of respiratory rate at 5,000 ppm and 10,000 ppm, tidal volume at 5,000 ppm, and minute volume at 5,000 ppm and 10,000 ppm.
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From page 90... ...
(1993b) exposed groups of six male English smoothhaired guinea pigs to HC!
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From page 91... ...
Nose-breathing rats exposed to HCl (actual concentration 1,293 ~ 36 ppm) exhibited severe, necrotizing rhinitis, turbinate necrosis, thrombosis of nasal submucosa vessels, and pseudomembrane formation in the anterior portion of the nasal cavity.
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From page 92... ...
HCl concentrations were determined continuously using ion-specific electrodes. Animals were sacrificed 24 h post-exposure, and the upper respiratory tract was examined histologically.
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From page 93... ...
Exposure to HCl at 475 ppm and 2,550 ppm caused 10% and 40°/O decreases in respiratory frequency, respectively, that were accompanied by compensatory increases in pressure. Four mice exposed at 475 ppm died within 90 ~ post-exposure, and all mice exposed at 2,550 ppm died by day 14 post-exposure.
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From page 94... ...
is a sensory and respiratory irritant and causes changes in the upper respiratory tract at relatively low concentrations and short exposure times. As concentrations and exposure times increase, effects progress to the lower respiratory tract and may involve pulmonary edema and histopathologic changes.
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From page 95... ...
is a respiratory irritant and is corrosive. When inhaled, it solubilizes in mucous present in the nasal passages, and when the scrubbing mechanism ofthe upper respiratory tract is saturated, it may enter the lower respiratory tract (NRC 1991~.
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From page 96... ...
Morris and Smith (1982) also showed that at concentrations up to 226 ppm, >99.7°/0 of inspired HF might be scrubbed in the upper respiratory tract of the rat.
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From page 97... ...
The relationship is similar for the mouse within this time period (2.2-3.2 times) ; however, for respiratory irritants such as HCI, the mouse "may not be a good model for extrapolation to humans," because "mice appear to be much more susceptible to the lethal effects of HCl than other rodents or baboons....To some extent, this increased susceptibility may be due to less effective scrubbing of HCl in the upper respiratory tract" (NRC 1991~.
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From page 98... ...
That increased susceptibility might be due to less effective scrubbing of HC! in the upper respiratory tract of mice compared with rats (NRC 1991~.
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From page 99... ...
(1976) examined the hazard of simultaneous acute inhalation exposure to HCI, HE, and alumina dust, which are components of solid rocket motor exhaust.
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From page 100... ...
(1942) exposed three rabbits, three guinea pigs, and one monkey to HCl at 34 ppm for 6 in/d, 5 d/wk for 4 wk.
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From page 101... ...
uptake and exacerbate irritation, those asthmatic subjects are considered a sensitive subpopulation. Therefore, because the test subjects were a sensitive subpopulation and the end point was essentially a no-effect level, no uncertainty factory (UF)
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From page 103... ...
Using the default value of 10 for interspecies variability would bring the total adjustment to 100 instead of 30. That would generate AEGL-2 values that are not supported by data on exercising asthmatic subjects, an especially sensitive subpopulation.
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From page 104... ...
. The prediction that humans would be disabled by exposure for 4 h or ~ h to 3.6 ppm cannot be supported when exercising asthmatic subjects exposed to one-halfthat concentration for 45 min exhibited no effects.
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From page 105... ...
7.2. Summary of Animal Data Relevant to AEGL-3 Baboon exposure studies involving an escape performance test and pulmonary function tests resulted in effects consistent with those defined by AEGL-3 (Kaplan 1987; Kaplan et al.
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From page 106... ...
AEGL-3 values generated from a total UF of 30 would be close (within a factor of 2) to the AEGL-2 values generated from data on exercising asthmatic subjects; (3)
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From page 107... ...
A NOAEL for sensory irritation in exercising asthmatic subjects was used for AEGL-1. Severe nasal and pulmonary effects in rats and a modification of the mouse RD50 were used for AEGL-2.
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From page 108... ...
The ERPG-2 for HC1 is based on animal studies suggesting serious eye and respiratory irritation above 20 ppm and below 100 ppm. The ERPG-3 is the maximum airborne concentration below which it is believed nearly all individuals could be exposed for up to 1 h without experiencing or developing life-threatening health effects.
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From page 109... ...
(NRC 1991~. gEEGL (emergency exposure guidance level)
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From page 110... ...
1988. Increases in airway responsiveness following acute exposure to respiratory irritants: Reactive airway dysfunction syndrome or occupational asthma?
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From page 111... ...
1974. Acute toxicity in rats and mice exposed to hydrogen chloride gas and aerosols.
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From page 112... ...
1989. Relative acute toxicities in the respiratory tract of inhaled hydrogen fluoride, hydrogen bromide,and hydrogen chloride.Toxicologist 9:36.
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From page 113... ...
1991. Relative acute toxicities of hydrogen fluoride, hydrogen chloride, and hydrogen bromide in nose- and pseudo-mouth-breathing rats.
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From page 114... ...
Time-scaling: Cat x t = k (ten Berge 1986~; (1.S ppm) ~ x 0.75 h = 1.35 ppm h Uncertainty factor: 10- min.
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From page 115... ...
effects in rats exposed at 1,300 ppm for 30 min. Time-scaling: C~ x t = k (ten Berge 1986~; (1,300 ppm)
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From page 116... ...
116 ACUTE EXPOSURE GUIDELINE LEVELS Uncertainty factors: 3 for intraspecies variability 3 for interspecies variability 10-minAEGL-3: Cat x 0.167h= 1,041 ppmh C= 6,234 ppm 10-min AEGL-3 = 6,234 ppm 10 = 623.4 ppm 30-minAEGL-3: Cat x 0.5 h= 1,041 ppmh C=2,082ppm 30-min AEGL-3 = 2,082 ppm 10 = 208 ppm I-hAEGL-3: Cat x 1 h= 1,041 ppmh C= 1,041 ppm 1-hAEGL-3= 1,041 ppm 10= 104.1 ppm 4-h AEGL-3: Cat x 4 h = 1,041 ppm h C= 260.25 ppm 4-h AEGL-3 = 260.25 ppm 10 = 26 ppm S-h AEGL-3 = 4-h AEGL-3 = 26 ppm
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From page 117... ...
Effects assessed included sore throat, nasal discharge, cough, chest pain or burning, dyspnea, wheezing, fatigue, headache, unusual taste or smell, total respiratory resistance, thoracic gas volume at functional residual capacity, forced expiratory volume, and forced vital capacity. All subjects continued the requisite exercise routine for the duration of the test period.
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From page 118... ...
Therefore, confidence in the AEGL values derived is high.
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From page 119... ...
That would generate AEGL-2 values that are not supported by data on exercising asthmatic subjects, an especially sensitive subpopulation because exercise increases hydrogen chloride uptake and exacerbates irritation. No effects were noted in exercising young adult asthmatic subjects exposed to HC1 at 1.8 ppm for 45 min (Stevens et al.
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From page 120... ...
AEGL-2 values for 1-h exposure period was based on extrapolation from the 30-min value. The 4- and 8-h AEGL-2 values were derived by applying a modifying factor of 2 to the 1-h AEGL-2 value because time scaling would yield a 4-h AEGL-2 value of 5.4 ppm and an 8-h AEGL-2 of 2.7 ppm, close to the 1.8 ppm tolerated by exercising asthmatic subjects without adverse health effects.
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From page 121... ...
AEGL-3 values generated from a total uncertainty factor of 30 would be close to the AEGL-2 values (within a factor of 2) generated above which are reasonable when compared with data on exercising asthmatics; (3)
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From page 122... ...
Thus, the total uncertainty factor is 10. Modifying factor: Not applicable Animal to human dosimetric adjustment: Insufficient data Time scaling: cn X t = k where n = 1, based on regression analysis of rat and mouse mortality data (1 min to 100 min)
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