1.1 Background of Study
One of the ubiquitous sets of chemicals that abound in the environment is the polycyclic aromatic hydrocarbons (PAHs), also known as the poly nuclear aromatic hydrocarbons. PAHs constitute a large class of organic compounds, containing 2 or more fused aromatic rings made up of carbon and hydrogen atoms. Food is one source of PAH (Guillen et al., 1997). When food particularly meat products and fish is smoked, roasted, barbecued, or grilled; PAHs are formed as a result of incomplete combustion or thermal decomposition of the organic materials (WHO, 2006). Pyrolysis of the fats in the meat/fish generates PAH that become deposited on the meat/fish. PAH production by cooking over charcoal (barbecued, grilled) is a function of both the fat content of the meat/fish and the proximity of the food to the heat source (Phillips, 1999; Kazerouniet al., 2001). Several analyses of charcoal roasted/grilled common food items have proven the presence of PAHs such as benzo[a]pyrene, anthracene, chrysene, benzo[a]anthracene, indeno[1,2,3-c,d]pyrene (Linda et al., 2011).
PAHs are produced in food when the fat from meat, poultry or fish drips onto hot coals or stones resulting in smoke and flare-ups which are carried back onto the grilled food. The amount and types of PAHs produced depend on the type of food, cooking method, temperature and cooking time. PAHs which formed in processed and cooked foods are very well known ecotoxicants (genotoxic substance) which are harmful to health. In mammalian cells PAH undergoes metabolic activation to diol epoxides that binds covalently to cellular macromolecules, including DNA, thereby causing errors in DNA replication and mutation that initiates the carcinogenic process. A number of PAHs have been found to have carcinogenic and mutagenic effects while some of them may act as synergists.High PAH has been reported in charcoal grilled/barbecued foods (such as fatty meat and meat products grilled under prolonged and severe conditions).
One of the major routes of humanexposure to PAHs in non-smoking people is food.These compounds can reach the food chain bydifferent ways as PAHs have been found in differentfood products, such as dairy products, vegetables,fruits, oils, coffee, tea, cereals and smoked meat,therefore the analysis of PAHs in food is a matter of concern (Plaza-Bolanoset al., 2010). Over the years,different sources of PAH contamination of food havebeen found. Food items and products could becontaminated by soils, polluted air and water (WHO,2005). Some aquatic food products, such as fish, canbe exposed to PAHs present in water and sedimentsand the PAH content greatly depends on the ability ofthe aquatic organisms to metabolize them. On the other hand, PAHs arealso found in foods as a result of certain industrialfood processing methods such as smoke curing,broiling, roasting and grilling over open fires orcharcoal which permits the direct contact betweenfood and combustion products (Silva et al., 2011).
It has been found that raw foods do not usually contain high levels of PAHs, presence of PAHs in uncooked food, such as vegetables, seeds and grains have been found to accumulate on the waxy surface of many vegetables and fruits. In general, PAHs are not present individually but in mixtures. Sixteen PAHs are considered priority pollutants in terms of health effects, included in US EPA’s list of 188 hazardous air pollutant: naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, indeno(1,2,3-cd)pyrene, dibenz(a,h)anthracene and benzo(g,h,i)perylene (US EPA, 1990, WHO,1998). Of these 16 PAHs, Benzo(a)pyrene (BaP) is probably the most studied and has been described by the International Agency for Research on Cancer (IARC) as probable human carcinogen in 1987 (IARC, 1987).
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