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 PAH 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 PAH level. That said, people love
barbecued foods may take in more PAHs.
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. Three PAHs
are classified as “probably carcinogenic”
to human (i.e. Group 2A) by the International
Agency for Research on Cancer of the World Health
Organization and are of more concern, but none
of the PAHs is classified as carcinogenic to humans
(i.e. Group 1).
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 intake which is without risk.
The Joint FAO/WHO Expert Committee on Food Additives
is of a view that exposure to PAHs should be as
low as practicable.
Local Study on PAHs
The Food and Environmental Hygiene
Department has conducted a study on PAHs. 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 will 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.
For consumers
Do not overindulge in barbecued
meats;
Do not eat 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.
Last
review date: 19-01-2005