Airborne contamination assessment

USEPA] US Enviromnental Protection Agency. 2003. Western Airborne Contaminants Assessment Program Research Plan, EPA/600/R-03/035, May 2003. 

However, assessing occupational exposure to airborne contaminants in a representative way is not an easy task and requires a good deal of professional judgment and reliance on a good methodology. There are many issues to be resolved, such as... 

Personal exposure Predictions of exposure of occupants to airborne contaminants for risk assessment, inhaled doses, or time-integrated concentration values. 

Scenario Development and Simulation The typical procedure for assessing the consequences of an airborne contaminant release is as follows ... 

Petty, J.D. Gale,R.W. Huckins, J.N. Cranor, W.L. A1 varez, D. A. Clark, R.C. 2000,Development and Application of Techniques for Sampling Bioavailable Airborne Contaminants-Tentatively Identified Compounds by Gas Chromatography/Mass Spectrometry. USGS Colirmbia Environmental Research Center Colirmbia, MO Unpublished report to U.S. EPA National Exposure Assessment Laboratory Las Vegas, NV. 

Reinmuller, B. (2000), Microbiological risk assessment of airborne contaminants in clean zones, Bulletin No. 52, Royal Institute of Technology/Building Services and Engineering, Stockholm. 

Two types of sampling monitors are in general use air samples are used to assess the airborne contamination levels at selected points. In the case of particulate materials a volume of air is drawn through a filter paper on which the particulates are deposited. An alarm may be set on increase of activity. 

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. 

The present purpose is to set down some guidelines for assessing the dry flux of acidic airborne contaminants to natural surfaces, and to discuss their limitations. For now, this dry flux will be taken to include all turbulent transfer of aerosol not associated with rainfall the reason for the subtlety will become apparent later. The matter will be considered in the light of three questions (a) how much acidic aerosol is present in air,... 

An air sample collected in the breathing zone of employees to assess their exposure to airborne contaminants. 

In a conventional laboratory, Adeloju and Bond [42] observed considerable variations when periodically measuring voltammetrically standard solutions of cobalt, nickel, copper, zinc, selenium, and lead owing to the variability of airborne contamination. They stress that the adoption of a blank substraction approach is no more than a futile exercise because of the variability of the analytical blank levels with time. Boutron [43] assessed the effect of air purity on the analysis of a standard solution containing 10 ng/mL of iron. When samples were prepared in an ordinary laboratory environment, values of 20.6 ng/mL were observed Finally, Gretzinger et al. [44] filled carefully cleaned quartz beakers (cross-section, 16 cm volume 20 mL) with 10 mL of 1 M HCl, prepared by subboiling (or nonebullient) distillation [45], deposited them uncovered in an ordinary laboratory on different days, and measured the iron level in the HCl solution. The weather was found to play an important role as a rule, when it is raining the air is essentially more pure than when it is dry. On one dry day, the amount of iron in the 10 mL of 1 M HCl over a periode of 6 hr was up approximately 20 ng, on another up to more than 30 ng. 

Routine surveys should be conducted to assess workplaces for radiation dose rate, surface contamination and airborne contamination. The survey should demonstrate that the work environment is satisfactory for continued operation and that no change has taken place that would call for a reassessment of either zone designations or operating procedures. Factors that may affect the type and frequency of each of these surveys will include ... 

Ma, R., Beilis, D., and McLeod, C. W. (2000) Isotopic analysis of uranium in tree bark by ICP mass spectrometry a strategy for assessment of airborne contamination. Anal. Chem., 72, 4878-81. 

The atmospheric fate of contaminants must be assessed whenever it is determined that significant gaseous or airborne particulate contaminants are released from the site. The atmospheric fate of contaminants released originally to other media, but eventually partitioned to the atmosphere beyond site boundaries, must also be assessed whenever this intermedia transfer is likely to be significant. 

Eduard, W. Fleederik, D. Methods for quantitative assessment of airborne levels of noninfectious microorganisms in highly contaminated work environments. Am. Ind. Hyg. Assoc. J. 1998, 59,113-127. 

The California Air Resources Board has prepared risk assessments for a number of toxic airborne compounds and mixtures, designated as toxic air contaminants, TACs (Table 16.15). For example, risk assessments for individual compounds such as benzene, benzo[a]pyrene (see Chapter 10), formaldehyde, and vinyl chloride have been carried out, in addition to complex mixtures such as diesel exhaust (California Air Resources Board, 1997a) and environmental tobacco smoke (California Environmental Protection Agency, 1997). These risk assessment documents form the basis for controls imposed as part of the risk management process (e.g., see Seiber, 1996). 

The human health risk assessment was conducted based on exposure estimates from two most relevant exposure pathways, namely dietary intake of POPs from food consumption and inhalation intake of airborne POPs contaminants. The potential intake of POPs from drinking water (considered to be a relatively minor exposure pathway) was not taken into account due to lack of relevant local data necessary for their estimation. 

Ambient (field blanks) are sample containers with PTFE-lined septum caps filled with analyte-free water in the field to establish whether contamination could have been introduced into water samples from ambient air during sampling. The laboratory provides a bottle of analyte-free water, and the field crew pours this water from the bottle into a sample container in a manner that simulates the transfer of a sample from a sampling tool into a container. Ambient blanks are analyzed for the contaminants of concern that may be airborne at the site in order to assess the sampling point representativeness. 

Finley BL, Kerger BD, Dodge DG, et al. 1996a. Assessment of airborne hexavalent chromium in the home following use of contaminated tapwater. J Expo Anal Environ Epidemiol 6(2)229-245. 

Acute. Exposures occur for relatively short periods of time, generally from minutes to one to two days. Concentrations of (toxic) air contaminants are usually Iiigli relative to dieir protection criteria. In addition to iiilialation, airborne substances might directly contact die skin, or liquids and sludges may be splashed on die skin or into die eyes, leading to adverse healdi effects. This subject area falls, in a general sense, in die domain of hazard risk assessment (HZRA) and is addressed in die next two Parts (IV and V) of tills book. 

---