Benzo emission

One of the most studied of the polyaromatic hydro-carbone (PAH) is benzo(a)pyrene (BaP), which is present in coal tar at coke oven plants. The BaP content of coal tar is between 0.1% and 1 % and it contributes to the serious potential health effects on employees exposed to coke oven emissions. The largest sources of BaP are open burning and home heating with wood and coal. The latter alone contributes 40 percent of all the BaP released each year in the USA. 

Whitaker JE, Haugland RP, Prendergast FG (1991) Spectral and photophysical studies of benzo[c]xanthenes dyes dual emission pH sensors. Anal Biochem 194 330-344... 

The presence of polycyclic aromatic hydrocarbons in the environment is of obvious concern and, apart from specific occupational environments, human exposure to these compounds derives from combustion products released into the atmosphere. Estimates of the total annual benzo[aJpyrene emissions in the United States range from 900 tons (19) to about 1300 tons (20). These totals are derived from heat and power generation (37-38%), open-refuse burning (42-46%), coke production (15-19%) and motor vehicle emissions (1-1.5%) (19,20). Since the vast majority of these emissions are from stationary sources, local levels of air pollution obviously vary. Benzo[aJpyrene levels of less than 1 pg/1,000 m correspond to clean air (20). At this level, it can be estimated that the average person would inhale about 0.02 pg of benzo[aJpyrene per day, and this could increase to 1.5 pg/day in polluted air (21). 

This is an area of strong continental climate with dry and hot summer and severe winter with strong winds that transport dust at short and long distance, for instance yellow sand phenomenon in northwest China. During air transport these soil particles absorb numerous pollutants-carcinogens, like benzo(a)pyrene and heavy metals (Ni, Cd, Co, Zn, Pb, As) both from industrial emissions into the atmosphere and waste landfill sites. 

SNARF and SNAFL indicators are benzo[c]xanthene dyes that can be described as semi-naphthofluoresceins and semi-naphthorhodafluors, respectively, depending on whether the benzo[c]xanthene ring is substituted at the 10-position with oxygen or with nitrogen, respectively (Whitaker et al., 1991). These indicators, whose p K l values are in the physiological range, exhibit distinct emission bands for the pro-tonated and deprotonated forms so that emission ratio measurements are possible. In SNAFL, the acidic form is more fluorescent, whereas in SNARF, the basic form is more fluorescent. 

Whitaker J. E., Haugland R. P. and Prendergast F. G. (1991) Spectral and Photophysical Studies of Benzo[c]xanthene Dyes Dual Emission pH Sensors, Anal. Biochem. 194, 330—44. 

J. E. Whitaker, R. P. Haugland, G. Predengast, Spectral and photophysical studies of benzo[c]xan-thene dyes Dual emission pH sensors, A nal. Biochem. 194, 330-344(1991). 

Some PAHs (e.g., phenanthrene, pyrene, and benzo[g,/z,i]perylene) are commonly seen in products boiling in the middle to heavy distillate range. In a method for their detection and analysis (EPA 8310), an octadecyl column and an aqueous acetonitrile mobile phase are used. Analytes are excited at 280 nm and detected at emission wavelengths of >389 nm. Naphthalene, acenaphthene, and fluorene must be detected by a less sensitive UV detector because they emit light at wavelengths below 389 nm. Acenaphthylene is also detected by UV detector. 

Schauer et al. (2001) measured organic compound emission rates for volatile organic compounds, gas-phase semi-volatile organic compounds, and particle-phase organic compounds from the residential (fireplace) combustion of pine, oak, and eucalyptus. The particle-phase emission rates of benzo [a]anthracene were 1.22 mg/kg of pine burned, 0.630 mg/kg of oak burned, and 0.533 mg/kg of eucalyptus burned. The gas-phase emission rate was 0.032 mg/kg of eucalyptus burned. 

California Phase 11 reformulated gasoline contained benzo[i]fluoranthene at a concentration of 280 pg/kg. Particle-phase tailpipe emission rate from a noncatalyst-equipped gasoline-powered automobile was 32.7 pg/km (Schauer et af, 2002). 

In 1978, the emission of benzo(a)pyrene (BaP) from an aluminum plant In the vicinity of Sundsvall, Sweden, was estimated to be about four times the total amount emitted from all the motor vehicles In that country. As might be expected, the result of this estimate caused considerable concern, and a survey of the air quality In the Sundsvall area was made In 1980-81. The program monitored concentrations of polycyclic aromatic hydrocarbons (PAH) and fluoride In ambient air, with samples being collected once each week. Concentrations of fluoride and meteorological data were measured by the aluminum company laboratory, while PAH concentrations were determined by the Norwegian Institute for Air Research (NILU). 

When epidemiological studies form the basis for the risk assessment of a single chemical or even complex mixtures, such as various combustion emissions, it may be stated that in those cases the effects of combined action of chemicals have been incorporated. Examples can, for instance, be found in the updated WHO Air Quality guidelines (WHO 2000). Thus, the guideline value for, e.g., ozone was derived from epidemiological studies of persons exposed to ozone as part of the total mixture of chemicals in polluted ambient air. In addition, the risk estimate for exposure to polycyclic aromatic hydrocarbons was derived from studies on coke-oven workers heavily exposed to benzo[fl]pyrene as a component of a mixture of PAH and possibly many other chemicals at the workplace. Therefore, in some instances the derivation of a tolerable intake for a single compound can be based on studies where the compound was part of a complex chemical mixture. 

Although the ultimate source of much of particulate organic matter (POM) in the urban aerosol appears to be fossil fuel a specific knowledge of the amounts and classes of organic compounds contributed by various types of sources is lacking. Estimates of source contributions have been based on emission inventories which have been largely directed toward polycyclic aromatic hydrocarbons and/or benzo(a)pyrene. There has been very little work on the development of mathematical and statistical models for POM source identification and allocation (1). In view... 

PAHs also generally have well-structured emission spectra (see Figs. 10.6-10.10) and relatively large fluorescence quantum yields. For example, in degassed n-heptane at room temperature, the fluorescence quantum yields are as follows fluoranthene, 0.35 benz[ ]anthracene, 0.23 chrysene, 0.18 BaP, 0.60 BeP, 0.11 and benzo[g/zi]perylene, 0.29 (Heinrich and Giisten,1980). Cyclopenta[crf]pyrene, however, does not fluoresce. 

Clearly, a sound evaluation of the total mutagenic/carcinogenic potencies of a complex mixture of POM emissions (e.g., diesel exhaust) should include not only the PEFs of the primary particle- and vapor-phase PAHs and PACs but also those of the mutagens formed in atmospheric reactions of precursor PAHs (see, for example, Arey et al. (1992), Lewtas (1993b), Atkinson and Arey (1994), Nielsen et al. (1996), Arey (1998a), and Section F). For examples of such formal scientific health risk assessments prepared by the State of California Air Resources Board and Office of Environmental Health Hazard Assessment, see Benzo[ ]pyrene as a Toxic Air Contaminant (CARB, 1994) and Identification of Diesel Exhaust as a Toxic Air Contaminant (CARB, 1998). 

In contrast, during the winter, the nonvolatile 5- and 6-ring PAHs BaP (Fig. 10.15b), benzo[6]fluoranthene, dibenzanthracene, benzo[g/t/]perylene, benzo[fc]fluoranthene, and indeno[o/]pyrene had 63-82% of their masses in the 0.05- to 0.5-/aiti range, primary emission mode I. However, as seen in Fig. 10.15c, the pattern shifts significantly to larger sizes for aerosols sampled in the summer. 

BaP, benzo[g/z/]perylene, benzo[6]fluoranthene, in-deno[l,2,3-cd]pyrene, and benzo[/c]fluoranthene, contribute the major portion of the identifiable mutagenicity of the extract of the whole unfractionated sample, accounting for 8.6, 2.5, 1.7, 1.4, 1.2, and 0.8%, respectively, of the total mutagenicity of the whole sample. Two semipolar mutagenic PACs were also present at significant levels 2-nitrofluoranthene, a product of atmospheric reactions, and 6//-benzo[c<7]pyren-6-one, a primary O-PAC pollutant present in exhaust emissions from diesel engines and non-catalyst-equipped cars (see Sections E and F). These account for an additional 0.8 and 1.6%, respectively, of the identified whole sample mutagenic potency (see Table 10.26). 

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