Risk of PAHs in Barbecued Meats
What are PAHs?
PAHs (polycyclic aromatic hydrocarbons) refer to a large group of organic chemicals containing rings of carbon and hydrogen atoms. PAHs are present everywhere in the environment as pollutant in air, soil, water and foods. They are formed during incomplete combustion of fuels and organic substances and are also present in vehicle emissions and tobacco smoke.
What are the sources of PAHs?
Food attribute to the major exposure (about 90%) to PAHs for non-smokers. However for smokers, significant contribution of PAHs exposure may be attributed to cigarette smoking. Since PAHs are ubiquitous in the environment, they are present in almost all food, although they are rarely found in high levels in raw foods. Cooking methods such as roasting and grilling, on the other hand, will generate more PAHs and result in higher levels of PAHs. Also, charred foods have a higher PAHs level. That said, people love barbecued foods may take in more PAHs.
Major dietary contributors of PAHs depend on the consumption pattern (amount and types of food consumed) and the levels of PAHs in foods. In general, cereals and vegetables (owing to high consumption in the diets), and fats and oils (owing to higher concentrations of PAH in this food group) were the major contributors to dietary exposure to PAHs. Generally, despite their usually higher concentration of PAHs, grilled/smoked/barbequed fish and meat making a relatively low contribution to PAHs, particularly as they are small components of the diet.
What are the health concerns of PAHs?
PAHs will undergo metabolic transformation in the human body and may form products that are excreted or active metabolites that may bind to DNA, the genetic materials inside the cell. The latter pathway is considered to be related to the cancer causing potential of PAHs. One PAH, benzo[a]pyrene, is classified as "carcinogenic to human" (i.e. Group 1 agent) and three PAHs namely, cyclopenta[cd]pyrene, dibenzo[a,l]pyrene, and dibenz[a,h]anthracene, are classified as "probably carcinogenic" to human (i.e. Group 2A agent) by the International Agency for Research on Cancer (IARC) of the World Health Organization.
Since cancer-causing potential is the concern and that some PAHs can damage genetic materials inside cells, it is not possible to define a level of exposure which is without risk. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) is of the view that exposure to PAHs should be as low as practicable. JECFA evaluated PAHs in 2005 and concluded that the estimated dietary exposure to PAHs were of low concern for human health. JECFA recommended some measures to reduce exposure to PAHs such as avoiding contact of foods with flames, and cooking with the heat source above rather than below the food.etc. European Food Safety Authority (EFSA) also assessed the dietary exposure to PAHs in 2008 and concluded that the estimated dietary exposure may indicate a low health concern for average consumer but a potential health concern for high consumer.
Local Study on PAHs
The Food and Environmental Hygiene Department has conducted a study on PAHs in 2004. Samples of barbecued meats (siu mei, namely roasted pork, BBQ pork and roasted ducks, and dried meats, namely dried beef and dried pork) were collected and analysed. We found that the higher the cooking temperature, the more PAHs would be generated; the closer the distance of the food from the heat source, the higher the PAH levels. Furthermore, PAH levels tend to be higher on the skin and fat portion (the outer part) of roasted ducks; and the cooking method of charcoal grilling gives rise to more PAHs in foods when compared with gas grilling and electric oven roasting methods. Having said that, we also observe that PAH levels in siu mei prepared by electric oven roasting and gas grilling are comparable to those found in other foodstuffs in other overseas studies. In other words, siu mei prepared in these ways is not a particular high risk food item.
How to reduce the risk?
With reference to the findings of our above-mentioned study, to minimise the risk of exposure, we have the following recommendations to the trade and consumers -
For the trade
- For making "Siu Mei", gas grilling or electric oven roasting is preferred to charcoal grilling. For making dried meat, electric grilling is preferred to gas grilling;
- Avoid direct contact of meats with flame and avoid fats from dripping onto the heat source (this can be done by trimming off visible fats before barbecuing and proper design of heating chamber); and
- Cook meats at the lowest possible cooking temperatures and avoid overcooking. However, the meat should be cooked thoroughly to destroy foodborne pathogens.
- Prior to grilling and roasting, the meat could be cooked partially by a method which employs a lower cooking temperature such as boiling.
- Avoid overindulging in barbecued meats;
- Avoid eating charred foods;
- Maintain a balanced and healthy diet by eating plenty of fruits and vegetables; and
- When going for barbecuing, trim visible fats before barbecuing; avoid foods from flame and fats from dripping onto the heat source; and pre-cook foods (e.g. by boiling) before barbecued.
Risk Assessment Section