Particle exposure level and potential health risks of domestic Chinese cooking
Introduction
Cooking oil fumes (COF) are a mixture of complex compositions generated from the intense chemical reactions when food is cooked with oil at a temperature up to 300 °C [1]. The main components of the oil fumes are fatty acids, alkanes, and olefins, followed by aldehydes, ketones, esters, aromatic compounds and heterocyclic compounds [2], [3]. A number of studies have detected the constituents of COF and discovered over 100 types of compounds among which carcinogenic polycyclic aromatic hydrocarbons (PAHs) and mutagenic heterocyclic amines (HCAs) are also in the list [4], [5], [6], [7].
Earlier measurements demonstrate an extremely high exposure level of both particulate and gaseous pollutants for cooks in commercial and domestic kitchens [8]. A real-time measurement in a Chinese food store showed elevated mass and number concentrations of fine particulate matter (PM2.5) by a factor of 12 and 85 respectively during cooking compared to non-cooking time [9]. A comparative study of Chinese, Malay and Indian cooking methods measured 16 priority PAHs, finding that high-temperature cooking like deep-frying and stir-frying generate higher molecular weight PAHs such as benzo [b]fluoranthene, indeno [1,2,3-cd]pyrene and benzo [g,h,i]perylene [10]. Meanwhile, a 24-h measurement in Taiwanese families also found a remarkably higher particle concentration during cooking hours [11]. Other family members may also experience 30–54% COF exposure with the kitchen door open [12]. The COF concentrations measured vary significantly with ingredients [13], cooking methods [14], [15], oil temperature [16] and fuels [8]. Furthermore, the deposition and coagulation of particles cause a highly uneven spatial distribution in the kitchen [17], [18], [19]. Particle concentrations, the size-dependent emission rate and the individual intake fraction of a simplified cooking process as heating oil, have been previously studied [20], [21], [22]. However, the lack of real-time measurements in cooks' breathing zone during a typical domestic Chinese cooking process impedes clear understanding of the personal exposure level.
A large number of epidemiological studies have proved the association between long-term COF exposure and increased morbidity and mortality. Among them, an increased risk of cancer has aroused the widest concern. Numerous case-control studies in Singapore, Hong Kong, Taiwan, Shanghai, Nanjing, and Gansu reveal that the risk of cancer is significantly correlated with cooking behavior [23], [24], [25], [26], [27], [28]. A recent study also found a dose-response relationship between lung cancer and COF exposure [29]. Other studies show that exposure to COF, especially with biofuels used, causes an increased risk of respiratory diseases such as lower airway infection in children [30], chronic obstructive pulmonary disease [31], tuberculosis [32] and asthma [33]. Cardiovascular risk has also been linked with daily cooking [34], [35]. The underlying mechanisms between COF exposure and these health risks remain unclear, though pathological studies suggest inflammatory processes and oxidative stress may play a major role [36], [37], [38]. Many researchers also appeal for further studies to identify relations between exposure levels and the adverse health effects.
Biomarkers, as signals reflecting organisms' biochemical changes after interaction with environmental factors, have been widely used in pathological studies. There are various biomarkers with respect to pulmonary volume and pulmonary ventilation function [39]. Reduced lung function is observed both in vulnerable populations chronically exposed to gas cooking [40] and healthy volunteers exposed to COF for a short time [41]. Fractional exhaled nitric oxide (FeNO) is an established biomarker that offers a non-invasive way to quantitatively measure respiratory inflammation [42] and shows high sensitivity to aerosol pollution [43], [44]. For assessing cardiovascular risks, brachial artery cuff blood pressure serves as an independent predictor of morbidity and mortality in hypertension, coronary heart disease, heart failure, stroke, and kidney disease [45], [46]. 1-Hydroxypyrene (1-OHP), the main metabolite of pyrene in mammals, is now a recommended and widely used biomarker for exposure to environmental PAHs [47], [48]. Its concentration in urine is significantly associated with the levels of environmental pyrene and total PAHs [49], [50]. 8-Hydroxy-2′-deoxyguanine (8-OHdG) is an oxidized nucleoside produced by cells after attacks by reactive oxygen species (ROS) while malondialdehyde (MDA) is a major product of membrane lipid peroxidation. They are both prevailing biomarkers for oxidative stress [51], [52], [53]. An elevated level of urinary 1-OHP, 8-OHdG and MDA was observed in professional cooks and housewives with long-term cooking experience [54], [55], [56]. However, whether these biomarkers associated with cardiopulmonary health and oxidative stress respond to short-term COF exposure in Chinese domestic cooking conditions is still unknown. In addition, the dose-response relationship between changes of biomarkers' levels and the intensity, time and frequency of exposure needs further study to better understand the health risks that result from cooking.
Therefore, we conducted this study in a controlled environment to obtain the actual personal COF exposure level during a typical domestic Chinese cooking and to further explore potential health risks resulting from short-term COF exposure at these levels. Performed in a kitchen chamber with most confounding factors eliminated, this study exhibited the representative particle exposure level during typical Chinese cooking in domestic kitchens under normal or poor ventilation conditions. Furthermore, it screened out proper biomarkers for COF exposure and unveiled their variation tendency, which contributed to further understanding the underlying mechanisms of the health hazards of COF exposure.
Section snippets
Subjects
6 voluntary university students participated including 3 males and 3 females, with an average age of 23.8 ± 0.3.
All participants were non-smokers without any clinically diagnosed chronic cardiopulmonary disease or allergy and they kept healthy during the whole period of the study. All of them claimed to acquire basic cooking skills but have few cooking experiences.
Experiment design
The experiment was conducted intensively in 4 consecutive days in December 2016 at Tongji University. Every participant was invited
Results
All of the 6 participants completed the whole study and remained healthy during the 4 days.
Discussion
Chinese cooking processes produce particulate matter and VOCs that cause an unfavorable domestic environment and pose a risk to the health of both cooks and other family members. However, the Chinese current standards of ventilation in kitchens only regulate the installation location and performance of exhausting hoods [61], [62], paying no attention to the exposure of the cooks during cooking. This controlled experiment in the kitchen chamber demonstrated that typical Chinese domestic cooking
Conclusions
This study in the kitchen chamber exhibited a notable exposure level to inhalable particles that cooks may experience during daily domestic Chinese cooking processes. Furthermore, the experiment demonstrated a significant reduction of lung function among young healthy students after two days' typical Chinese domestic cooking processes. However, a single short-term exposure to COF at around 20 min causes only modest cardiopulmonary, inflammatory health effects or oxidative stress which does not
Acknowledgement
This work was supported by National Science Foundation of China NO. 91543120, Shanghai Natural Science Fund No.14ZR1435600.
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