Elsevier

Chemosphere

Volume 50, Issue 5, February 2003, Pages 611-618
Chemosphere

Sources and patterns of polycyclic aromatic hydrocarbons pollution in kitchen air, China

https://doi.org/10.1016/S0045-6535(02)00668-9Get rights and content

Abstract

Twelve polycyclic aromatic hydrocarbons, multi-ringed compounds known to be carcinogenic in air of six domestic kitchens and four commercial kitchens of China were measured in 1999–2000. The mean concentration of total PAHs in commercial kitchens was 17 μg/m3, consisting mainly of 3- and 4-ring PAHs, and 7.6 μg/m3 in domestic kitchens, where 2- and 3-ring PAHs were predominant, especially naphthalene. The BaP levels in domestic kitchens were 0.0061–0.024 μg/m3 and 0.15–0.44 μg/m3 in commercial kitchens. Conventional Chinese cooking methods were responsible for such heavy PAHs pollution. The comparative study for PAH levels in air during three different cooking practices: boiling, broiling and frying were conducted. It was found that boiling produced the least levels of PAHs. For fish, a low-fat food, frying it produced a larger amount of PAHs compared to broiling practice, except pyrene and anthracene. In commercial kitchens, PAHs came from two sources, cooking practice and oil-fumes, however the cooking practice had a more predominant contribution to PAHs in commercial kitchen air. In domestic kitchens, except for cooking practice and oil-fumes, there were other PAHs sources, such as smoking and other human activities in the domestic houses, where 3–4 ring PAHs mainly came from cooking practice. Naphthalene (NA, 2-ring PAHs) was the most predominant kind, mostly resulting from the evaporation of mothball containing a large quantity of NA, used to prevent clothes against moth. A fingerprint of oil-fumes was the abundance of 3-ring PAHs. Heating at the same temperature, the PAHs concentrations in different oil-fumes were lard > soybean oil > rape-seed oil. An increase in cooking temperature increased the levels of PAHs, especially acenaphthene.

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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