Exposure to acid aerosols

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... 

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. 

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

Brauer M, Koutrakis P, and Spengler JD (1989) Personal exposures to acidic aerosols and gases. Environmental Science and Technology 23 1408. 

In general, the levels of U.S. population exposure to acid aerosols are quite modest in comparison with the levels at which health effects have been demonstrated. The most likely acid sulfate species appears to be NH HSO particle sizes depend on the age of the aerosol but are in the submicron range. Elevated concentrations of acidity are likely to persist at a given location for a few days, at most. Gaseous acidity levels are likely to equal or exceed particulate acidity levels in most locations. 

Spengler, J.D., et al. (1989), Exposures to acidic aerosols. Environ, Health Persp. 79 43-52. 

Wyzga, R.E., and F.W. Lipfert (1990), The Need to Reconcile Experimental and Ambient Exposures to Acid Aerosols, presented at the NAPAP 1990 International Conference on "Acidic Deposition State of Science and Technology," Hilton Head, SC, Feb. 1990. 

Nevertheless, considerable evidence snggests that particulate pollution contributes to exacerbations of asthma. Atmospheric particle levels have been linked with worsening of symptoms, decrements in limg function, increased hospital admissions for asthma, and increased medication use (31-33). Recent clinical studies demonstrate that exposure to ozone increases airway inflammation in patients with mild asthma (34,35). Whether exposure to ambient particles also exacerbates airway inflammation in asthma has not been demonstrated. However, two recent studies suggest that exposure to acid aerosols either followed by (36), or in combination with (37), ozone exposure may increase airway responsiveness to ozone in subjects with asthma, at concentrations of acid aerosol well below those known to cause changes in lung function or airway inflammation in the absence of ozone (38). 

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. 

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. 

Koutrakis, P., M. Brauer, S. L. K. Briggs, and B. P. Leaderer, Indoor Exposures to Fine Aerosols and Acid Gases, Environ. Health Perspect., 95, 23-28 (1991). 

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. 

Husain et al. studied the effects of CR and CN aerosols on clinical chemistry parameters (e.g., plasma glutamic-oxaloacetic tansaminase (GOT), plasma glutamic-pyruvic transaminase (GPT), acid phosphatase, and alkaline phosphatase). Rats were exposed via inhalation to aerosols of CR or CN. Animals exposed to CR aerosol exhibited no significant changes in plasma GOT and GPT activities or in acid and alkaline phosphatase activities. In contrast, CN-exposed animals manifested significant increases in GOT, GPT, acid phosphatase, and alkaline phosphatase activities. The conclusion drawn from the study was that exposure to CN aerosol could lead to tissue damage. 

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. 

Healthy subjects exposed to relatively modest concentrations of acidic aerosols experience accelerated clearance in large bronchi, but slower clearance in small airways (172-174). Interestingly, whereas macrophages from humans exposed to acidic aerosols have altered phagocytic function, acid exposures do not appear to induce an acute neutrophilic inflammation (175,176). Altered mucociliary clearance and phagoeytie eapability may render some individuals more sus-eeptible to infections, and contribute to the observed increase in morbidity associated with PM. 

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. 

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. 

Study of the possible health tffects of exposure to difunctional oxygenated organics (such as dicarboiylic acids) that ate present in urban aerosols. 

Repeated exposure of rats to an aerosol at a concentration of 470mg/m for 10 weeks caused only mild nasal irritation repeated exposure of rats to 77mg/m for 23 weeks resulted in elevated creatinine and boron content of the urine in addition to increased urinary volume. Conjunctivitis resulted when the dust was applied to the eyes of rabbits, probably the result of the exothermic reaction of boron oxide with water to form boric acid topical application of boron oxide dust to the clipped backs of rabbits produced erythema that persisted for 2-3 days. ... 

The exposure of soil to phosphorus aerosols will upset the pH of the soil and create a more acidic layer of soil. This decrease in pH often can exceed the buffering capacity of the surface layer of the soil depending upon the amount of applied phosphorus. This process can be mitigated by a larger soil volume area so that phosphorus speciation on a field scale will be minimal. The interaction of metals with phosphorus condensates could lead to their leachability and possible trace metal migration from the soil (Van Vorris et al. 1987). 

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 ... 

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