Acidic aerosol exposure

Norwood, D. M., Wainman, T., Lioy, P. J., and Waldman, J. M. (1992). Breath ammonia depletion and its relevance to acidic aerosol exposure studies. Arch, of Fa-wtron. Health 47, 309-313. 

A third study evaluated S04 and exposure to 24 children (ages were not provided) living in Uniontown, Pennsylvania (Suh et al. 1992). This study did not focus on ammonia exposure per se, but on other airborne contaminant concentrations in aerosols found outdoors, indoors, and by personal monitors. It sought to determine how personal exposures to these aerosols correlated with indoor and outdoor concentrations. Ammonia concentrations were measured in order to assess their potential for neutralizing found in aerosols. Ammonia was found to be in highest concentrations near the children (detected by the personal monitors), followed by indoor concentrations, and were minimal outdoors. It was proposed that a large proportion of the found in indoor aerosols are neutralized by NH3, and thus would lower the children s exposure to acid aerosols. The authors noted that more research is needed to fully model the influence of factors, including NH3, on indoor acid aerosol exposure. 

Lee MM, Schiireh S, Roth SH, Jiang X, Cheng S, Bjamason S, Green FHY. Effect of acid aerosol exposure on the surface properties of airway mucus. Exp Lung Res 1995 21 835 851. 

Health effects attributed to sulfur oxides are likely due to exposure to sulfur dioxide, sulfate aerosols, and sulfur dioxide adsorbed onto particulate matter. Alone, sulfur dioxide will dissolve in the watery fluids of the upper respiratory system and be absorbed into the bloodstream. Sulfur dioxide reacts with other substances in the atmosphere to form sulfate aerosols. Since most sulfate aerosols are part of PMj 5, they may have an important role in the health impacts associated with fine particulates. However, sulfate aerosols can be transported long distances through the atmosphere before deposition actually occurs. Average sulfate aerosol concentrations are about 40% of average fine particulate levels in regions where fuels with high sulfur content are commonly used. Sulfur dioxide adsorbed on particles can be carried deep into the pulmonary system. Therefore, reducing concentrations of particulate matter may also reduce the health impacts of sulfur dioxide. Acid aerosols affect respiratory and sensory functions. 

Utell, M. J. (1985). Effects of inhaled acid aerosols on lung mechanics an analysis of human exposure studies. Environmental Health Perspect. 63, 39-44. 

TI8. Schlesinger, R. B. (1989). Factors affecting the response of lung clearance systems to acid aerosols role of exposure concentration. E.nviron. Health Perspect. 79, 121-126. 

Information on the excretion of americium after dermal exposure in humans or animals is extremely limited. Some qualitative information is available from an accidental exposure in which a worker received facial wounds from projectile debris and nitric acid during an explosion of a vessel containing 241 Am (McMurray 1983). The subject also inhaled 241Am released to the air as dust and nitric acid aerosols, which was evident from external chest measurements of internal radioactivity thus, excretion estimates reflect combined inhalation, dermal, and wound penetration exposures (Palmer et al. 1983). Measurements of cumulative fecal and urinary excretion of241 Am during the first years after the accident, and periodic measurements made from day 10 to 11 years post accident indicated a fecal urine excretion ratio of approximately 0.2-0.3, although the ratio was approximately 1 on day 3 post accident (Breitenstein and... 

Concentrated hydrochloric acid is highly corrosive. Hydrochloric acid is primarily a concern in its aerosol form. Acid aerosols have been implicated in causing and exacerbating a variety of respiratory ailments. Dermal exposure and ingestion of highly concentrated hydrochloric acid can result in corrosivity. There is currently no evidence to suggest that this chemical is carcinogenic. 

Further study is needed of the phenomenon of kinetic limitations to the neutralization of acidic aerosols. Simultaneous occurrences of acidic aerosols at gaseous [NH3] well above the equilibrium values have been reported (56, 67), and it is still unclear whether kinetic limits to microscale neutralization or boundary layer mixing (macroscale) kinetics (or both) are responsible for these limitations. An understanding of the extent of human exposure to acidic aerosols, as well as of the availability of acidic aerosols for wet scavenging... 

In general polluted air consists of a mixed gas - aerosol complex containing varying concentrations of sulphur dioxide, S02 nitrogen oxides, NOx ozone, 03 and acid aerosols. Smith (1974) has suggested three categories of exposure of plants, in particular forest ecosystems, to atmospheric pollution ... 

Spengler JD, Koutrakis P, Dockery DW, et al. 1996. Health effects of acid aerosols on North American children Air pollution exposures. Environ Health Perspect 104(5) 492-499. 

The determination of susceptibility entails the presence of observable changes in biochemical or physiologic processes reflecting dose-response relationships unique to a chemical (e.g., sulfur dioxide) or class of chemicals (e.g., acid aerosols). Susceptibility and hypersusceptibility are not meaningful concepts outside of the context of specific exposures. "Dose-response relationships are chemical-specific and depend on modes of action people are not hypersusceptible to all kinds of exposures" (PCCRARM 1997). 

Epidemiology studies are limited in their ability to establish direct cause and effect relationships. Many confounding factors such as smoking, occupational exposure, and copollutants such as ozone may contribute to observed effects and, for this reason, investigators have exposed human volunteers and animals to acid aerosols under controlled conditions. 

Although pure sulfuric acid droplets are used almost exclusively in controlled exposures, ambient acid aerosols are chemically complex and are proposed to be composed of a core consisting of carbon, minerals, or heavy metals surrounded by acidic (sulfuric or nitric acid) surface material. Thus, knowing which chemical species is responsible for acid aerosol-induced adverse health effects is fundamental in developing proper control strategies for reducing air pollutants at their source. 

One of the most important issues in environmental epidemiology is accurate exposure measurement. Urban air pollution comprises several factors which may affect respiratory illness ozone, nitrogen dioxide, sulphur dioxide, acid aerosols, and particulates [316(NC)]. However, there is no evidence for increased air pollution contributing to increased prevalence of asthma [317(NC)]. 

Major metabolites of CS are 2-chlorobenzyl malononitrile, o-chlorobenzaldehyde and o-chlorohippuric acid, the glycine conjugate of o-chlorobenzaldehyde (Feinsilver el al., 1971 Leadbeater, 1973). Exposure of cats and rats to aerosols of CS results in absorption of the material with its presence being detectable in blood along with two metabolites, o-chlorobenzaldehyde and o-chlorobenzylmalononitrile (Leadbeater, 1973). Over a 1-h exposure of cats to 750 mg m 3 CS aerosol, the blood concentrations of CS and o-chlorobenzylmalononitrile rapidly reached plateau levels, but that of o-chlorobenzaldehyde continued to rise throughout exposure. Reducing the aerosol exposure concentration to cats by a factor of 10 did not produce a proportionate decrease in the blood... 

Data regarding exposure to mixtures of atmospheric contaminants indicate that, contrary to what might be expected, increased carbon dioxide concentration (up to 5% in air) does not alter the hyperventilatory rate induced by hyperammonemia in dogs (Herrera and Kazemi 1980). Ammonia in expired air may neutralize inhaled acid aerosols (EPA 1979 Earson et al. 1980 Utell et al. 1989). 

Suh HH, Spengler JD, Koutrakis P. 1992. Personal exposures to acid aerosols and ammonia. Environ Sci Technol 26(12) 2507-2517. 

In addition to nitrated PAHs, oxygenated derivatives include ketones, diones, quinones, and dicarboxylic acid anhydrides. Oxy- and nitro-PAH concentrations in the atmosphere are about an order of magnimde or less than their parent PAHs, yet they can account for a considerable degree of the toxicity and mutagenicity of urban aerosols. Exposure of PAHs to UV radiation in aquatic environments has been shown to produce significant phototoxicity to fish and invertebrates,and likely results from the formation of PAH photooxidation products. 

It is assumed that the deleterious effect of the sulfuric acid rather derives from the reduced pH-value than from the sulfate ion (ATSDR 1998). The hydrogen ion content of the aerosol is important for sulfuric acid toxicity. Following inhalation exposure, the extent of the toxicity is influenced by the duration and locality of contact of a sulfuric acid aerosol. 

Liu, B. Y. H., and Levi, J. (1980) Generation of submicron sulfuric acid aerosol by vaporization and condensation, in Generation of Aerosols and Facilities for Exposure Experiments, K. Willeke, ed., Ann Arbor Science, Ann Arbor, MI, pp. 317-336. 

For more or less all non-genotoxic carcinogens, a threshold limit value exists where there is no real risk of cancer. Taking this into account, some scientific associations have defined additional categories of carcinogenic substances which have no real carcinogenic potential below their occupational exposure limit. Well-known examples of such substances include sulfuric acid aerosols, hexachloro-benzene, trichloromethane, tetrachloromethane, lindane, dioxane, and 2,3,7,8-tet-rachlorodibenzodioxin (TCDD). 

Symptoms of acute sulfuric acid aerosol injury. Typical symptoms of short te m, single exposure sulfuric acid aerosol injury (about 100 mg m x 8 hours) is very similar to that caused by gaseous fluoride on broad leafed plants and consists of marginal and tip necrosis (Figures lA and IB). All plant species examined developed similar symptoms and they appeared to vary, only in degree, based upon species and plant sensitivity. Microscopic injury from sulfuric acid aerosol was found t be similar to that caused by simulated acidic precipitation. Guard cells and epidermal cells appeared shrunken and collapsed. 

Preliminary investigations of plant responses to longer term, lower concentration exposures indicate that symptoms associated with acute and chronic exposure may be quite different. Pinto bean exposed tc submicron sulfuric acid aerosol at concentrations of 1-5 mg/m for periods of several days developed a bifacial, interveinal necrosis very similar to that caused by sulfur dioxide. 

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