Concentrations in ambient air

Because of the low rates of molecular diffusion, assessment of workplace air quality using passive samplers usually entails sampling for a working shift, and exposure periods of one to four weeks tend to be needed to measure concentrations in ambient air. 

Acrylonitrile has not been found to occur at measurable concentrations in ambient air (Brodzinsky and Singh 1983). Measurable levels of atmospheric acrylonitrile are associated with industrial sources. 

Odour Determination in Ambient Air by Inspection Panels 3781 Odour Dispersion and Odour Concentration in Ambient Air... 

Exposure Levels in Environmental Media. Several studies are available documenting bromomethane concentrations in ambient air (Brodzinsky and Singh 1983 Harsch and Rasmussen 1977), but data for bromomethane in water are rare. Bromomethane has been analyzed for, but rarely detected, in foods (Daft 1987, 1988, 1989). Human exposure levels of bromomethane by inhalation of urban air have been calculated (Singh et al. 1981b). However, these levels are based on monitoring data more than 10 years old. Since urban air concentrations of bromomethane may have decreased due to reduced emissions from automobiles, exposure levels calculated from past data should be taken as an upper limit, and new levels calculated from current monitoring data would be useful. 

Figure 12.2 Response of a 4-mercaptobenzoic acid (4-MBA)-coated silicon cantilever to PETN vapors of 1.4-ppb concentration in ambient air. The solid curve depicts the bending response, and the dots depict the resonance frequency of the cantilever.

Fluoride concentrations in ambient air were studied by Thompson et al. [29] from 1966 to 1968. A total of 2164 samples were taken in non-urban and 9175 in urban areas. 98.5% of those from non-urban areas contained less than 0.05 pg/m, 1.3% contained 0.05-0.09 pg/m and only 0.1% contained 0.1-0.99 pg/m of fluoride. Levels in urban areas were slightly higher, 87.8% of samples containing less than 0.05 pg/m, 4.2% containing 0.05-0.09 pg/m, 7.7% containing 0.10-0.99 pg/m and 0.2% more than 1.00 pg/m of fluoride. The maximum concentrations observed were 0.16 from non-urban and 1.89 pg/m from urban locations. 

Even taken qualitatively, these reactivity data have important toxicological as well as chemical implications regarding the composition of PAHs and PACs in and on the surfaces of aerosols in polluted air parcels, both near-source and during transport (downwind). Thus, under certain conditions (e.g., daytime, summer season, and high oxidant levels) over a period of hours BaP concentrations in ambient air could be expected to decay dramatically as a result of reactions, while those of the benzofluoranthenes and indeno[l,2,3-cabsolute concentrations also change as a result of dilution of the air parcel caused by increased mixing depth over time and transport. However, impacts of such physical processes are minimized if one considers ratios of concentrations of reactive to nonre-... 

Arey, J., B. Zielinska, R. Atkinson, and A. M. Winer, Polycyclic Aromatic Hydrocarbon and Nitroarene Concentrations in Ambient Air during a Wintertime High-NO, Episode in the Los Angeles Basin, Atmos. Environ., 21, 1437-1444 (1987). 

Developing control strategies for ozone is very different than for relatively unreactive species such as CO. In the latter case, the concentrations in air are a direct result of the emissions, and all things being equal, a reduction in emissions is expected to bring about an approximately proportional reduction in concentrations in ambient air. However, because O, is formed by chemical reactions in air, it does not necessarily respond in a proportional manner to reductions in the precursor emissions. Indeed, as we shall see, one can predict, using urban airshed or simple box models, that under some conditions, ozone levels at a particular... 

Vainiotalo, S., Y. Peltonen, and P. Pfaffli, MTBE Concentrations in Ambient Air in the Vicinity of Service Stations, Atmos. Environ., 32, 3503-3509 (1998). 

Acrylonitrile has not been detected to occur at measurable concentrations in ambient air. Measurable levels of atmospheric acrylonitrile are associated with industrial sources. Mean 24-h aciylonitrile concentrations in atmospheric samples collected within 5 km of factories producing or using acrylonitrile ranged from less than 0.1 to 325 j,g/m3. The occurrence of acrylonitrile was correlated with wind patterns the highest concentrations were downwind of and in close proximity to the plant. The median concentration of aciy lonitrile for 43 measurements in source-dominated areas (i.e., near chemical plants) was 2.1 jig/m (Agency for Toxic Substances and Disease Registry, 1990). 

Reactive Species Concentration in Ambient Air (molec cm"3) Rate Constant" (cm3 molec"1 sec" ) ... 

Road transport is an important contributor to primary emissions of PM (soot, wear particles and road dust) and also a source of secondary particles formed by condensation of gaseous species (mainly S- and N-compounds and organics) emitted by the tailpipe and partly also by the wear of brakes and tyres. Thus, PM emissions from road traffic are responsible for an important proportion of the exceedances of the PM10 and PM25 Air Quality Limit Values established by the European legislation for the protection of the human health (2008/50/EC [17]). The daily (50 pg m-3) and annual (40 pg m 3 ) limit values for PM10 (atmospheric particles with mean aerodynamic diameter <10 pm) and the annual limit value for PM2.5 (25 pg m-3) (in force from 2015) concentrations in ambient air are indeed exceeded mostly in the urban areas (Fig. 1 [17]). 

Similarly, SVOC emissions are traditionally considered to present a lower risk because their vapor-phase concentration in ambient air is, by definition, very low. 

Toluene is a colorless liquid boiling at 101.4°C. Gasoline is 5 to 7% toluene and is the most common source of human exposure to toluene. Toluene is one of the most common solvents inhaled by solvent abusers. It is classified as moderately toxic through inhalation or ingestion and has a low toxicity by dermal exposure. Concentrations in ambient air up to 200 ppm usually do not result... 

Beeause CO concentration in ambient air and at workplaees is usually quite low, reliable methods for sample eolleetion and transport as well as highly sensitive methods for its measurement are needed (IPCS, 1999 Smith and Nelson, 1973). The sampling method reeommended by WHO (IPCS, 1999) comprises a sample introduetion system... 

Dichloroethane was not seen at a detection limit of 5 ppt in ambient rural air samples taken in southeastern Washington state (Grimsrud and Rasmussen 1975). It has been found at higher concentrations in ambient air samples from urban areas of the United States. Brodzinsky and Singh (1983) tabulated atmospheric levels at urban, rural, and industrial sites across the United States and reported a median concentration of 55 ppt. Pellizzari (1982) reported the detection of low levels (unspecified concentrations) of the compound in the vicinity of the Baton Rouge industrial area. 

In 12 workers who were occupationally exposed to ethylene oxide during the sterilization of medical equipment, concentrations of 0.2-8.5 ppm were detected (2). This study also confirmed the relation between the ethylene oxide concentration in ambient air and the amount of A-2-hydroxyethylvaline in human globin, which has been used as a biological marker of carcinogenicity. 

Another proposed regulatory approach takes into account the formaldehyde concentration In ambient air. There, two cases exist The exposure limit values on workplaces, and the exposure limit values in housing, which are generally one tenth of the workplace value, see Table III ... 

A very few fluorine-containing substances are, on the other hand, extremely toxic. The most (in)famous of these are fluoroacetic acid (ID50 4.7 mg kg in rats, IDioo 5 mg kg in humans [33] - the doses after which 50% or 100%, respectively, of the tested individuals die) and perfluoroisobutene (IC50 < 1 ppm - the concentration in ambient air for 4 h after which half of the tested individuals die). 

Loranger S and Zayed J. 1994. Manganese and lead concentrations in ambient air and emission rates from unleaded and leaded gasoline between 1981 and 1992 in Canada A comparative study. Atmos Environ 28 1645-1651. 

Buildings involved in chemical manufacture of 2,4,5- T contain about 1-50,000 ng/m. Buildings contaminated by PCB fires contain about 1-1,000 ng/m of 2,3,7,8- TCDD equivalents. PCDD concentrations in ambient air are below the detection levels of several pg/m. However, continued increases in the sensitivity of analytical procedures are allowing detection of 0.2 pg/m in some urban air samples. 

The lower vapour pressure of these compounds means their concentration in ambient air will also be low. If explosives are contained in an enclosure with cool surfaces the vapour concentration may be even lower than saturated values due to partitioning effects. The saturated equilibrium ambient air concentration of TNT, RDX, and PETN as a function of ambient temperature is shown in Figure 4. At room temperature there are approximately 100 picograms of TNT per mL available for detection. NG and DNT have even higher concentrations available for detection. Flowever, PETN and RDX produce less than 1 picogram per mL and hence are much more difficult to detect as vapours. For these compounds it is easier to use a wipe to extract material from surfaces and then to desorb thermally the compounds as vapours into the detection system. 

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