Sources and patterns of polycyclic aromatic hydrocarbons pollution in kitchen air, China
Introduction
Indoor air quality is of particular interest in the world. PAHs pollution in indoor air of Hangzhou, China has been surveyed with the result showing that the PAHs concentrations in indoor air were significant higher than those in corresponding outdoor air, indicating significant indoor sources of PAHs. With the different functions and ventilation conditions, the concentrations of PAHs in indoor air were: bedroom > kitchen > living room > balcony (Liu et al., 2001). Indoor air of kitchen is polluted by PAHs that come from not only outdoor air but also indoor emission sources such as cooking, gas home appliances. Air pollution in Chinese kitchens is serious because of the conventional cooking process.
Except for cooking practice, cooking oil-fumes should make a significant contribution to PAHs concentrations of indoor air including two parts: (1) once heated PAHs evaporate from the polluted oil into air; (2) at high temperature organic compounds are partially cracked to smaller unstable fragments (pyrolysis), mostly radicals recombine to give relatively stable PAHs (pyrosynthesis) (Moret and Conte, 2000). Epidemiological studies show an elevated incidence of cancers among non-smoking women with long-term exposure to cooking oil-fume (Gallanger and Ewood, 1964; King and Haenszel, 1973) and an excessive bladder cancer rate among cooks exposed to kitchen air (Schoenberg et al., 1984). This study thus was intended to ascertain whether different methods for cooking food and oil-fume contribute to different PAH patterns in kitchen air and to determine the contribution of each source to the overall levels of PAHs, so as to control PAHs pollution effectively.
A variety of efforts, including development of the chemical mass balance (CMB), have been made in recent years to understand the relationship between sources of PAHs and their concentrations in indoor air (Scheff et al., 1984). CMB models use the chemical and physical characteristics of sources and receptors to both identify the presence of and to quantify the source contribution to the receptor (Gordon, 1988), which requires a priori knowledge of the source signatures for a given area. Oil-fume is not only a significant source of PAHs in kitchen but also a potential one in other indoor facilities, such as bedrooms and living rooms, where little information is currently available to document the sources and levels of PAHs. The detailed PAHs composition of oil-fumes has not been determined previously. Once comprehensive information on the molecular composition of such fumes is available, it may be possible to estimate the contribution of cooking operations to the ambient air.
In this study, the molecular composition of the PAHs from oil-fumes is examined. Emissions from oil-fumes are quantitatively evaluated using an optimized method for sampling and analyzing PAHs in air (Liu et al., 2001).
Section snippets
Sampling sites
The PAH levels in kitchens’ air were influenced by the cooking methods, the fuels used for cooking and ventilation conditions. In order to understand PAHs generation in kitchens, six representative homes and four commercial kitchens (two were in 3-star hotels and two 4-star hotels) in Hangzhou were surveyed. Table 1 gives a descriptive profile of the sampling commercial kitchens, and domestic kitchens in detail. All kitchens were ventilated for 24 h with all doors and windows open before air
Levels of PAHs produced by different cooking practices
Emission from different cooking practices differ much. The levels produced by different cooking practices were measured to determine whether conventional Chinese cooking method was responsible for PAHs pollution in kitchens. The chemical composition of meat smoke aerosol was examined by Rogge et al. (1991). In this study, each PAHs produced during each process were determined by averaging the sum concentrations of PAHs in the gas and particle phases for individual samples (in Table 2). As was
Conclusion
The average concentration of 12 PAHs in air of hotel and commercial kitchens of Hangzhou was 17 μg/m3, which comprised mainly of 3- and 4-ring PAHs. The corresponding average in domestic kitchens was 7.6 μg/m3 and consisted mainly of 2- and 3-ring PAHs. NA was more abundant in domestic kitchen air than in commercial kitchen air. Food boiling produced the least amount of PAHs. The high-fat food produced more PAHs when broiled, so did low fat-level food when fried except PY and AN. In commercial
Acknowledgements
This project was supported by the Science and Technology Department of Zhejiang Province (No. 97-2-087).
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