Studies On The Assessment And Simulation Of Dietary And Environmental Exposures To Polycyclic Aromatic Hydrocarbons In Complex Matrices

ABSTRACT

Polycyclic aromatic hydrocarbons (PAHs) are known for their carcinogenic and mutagenic properties. They are formed from incomplete combustion of organics such as fossil fuels among others. PAHs are found in foods and in the environment. In this study, the concentration of PAHs and their potential risks were determined in smoked fishes, roasted foods, soils and plant samples in the Lagos metropolis, Nigeria. Smoked and raw fishes (Arius heude loti (catfish), Cynoglossus senegalensis (sole), Hake Sp (fresh stock fish)), raw and roasted corn (Zea mays), ripe and unripe plantain (Musa paradisiaca), yam (Dioscorea sagittifolia), plants grown on contaminated soils and soils from activity impacted sites were investigated for their levels and risk of PAHs. The fishes and food were extracted for PAHs by ultrasonication, and analysed using a HPLC (Agilent 1100 model HPLC system coupled to ultraviolet detector (HPLC-UV)). The soil and plant extracts were analysed by a gas chromatograph (GC) (Agilent 6890N GC) equipped with a mass selective detector (MS) (Agilent 5975 MS). The results showed that smoked fish samples (Hake Sp, Cynoglossus senegalensis and Arius heudeloti ) processed by charcoal fire gave the lowest sum of PAHs (121, 176 and 1136 µg/kg respectively). Followed by the firewood (781, 1258 and 1321 µg/kg respectively), while the sawdust method had the highest sum of PAHs (856, 1395 and 2058 µg/kg respectively). Based on the mean daily intake (MDI) risk assessment approach consumption of smoked fishes possessed some risks. However, based on the 5.0 μg/kg benzo(a)Pyrene (BaP) maximum level for smoked meat and fish established by the European Commission, no risk was associated with the consumption of the smoked fishes. Higher levels of PAHs were found in the roasted food samples compared with the raw samples. The sum of PAHs for raw and roasted food samples ranged between 0.19 - 0.53 mg/kg and 3.62 – 40.33 mg/kg respectively with roasted ripe plantain having the highest concentration. Based on a comparison with limits for roasted foods, the results from this study showed no potential risk associated with the ingestion of the foods. However, using the benzo (a) pyrene equivalence dose (BaPeq) approach to risk assessment, more risk were associated with the consumption of roasted foods compared to the non roasted foods. The sum of PAHs from the soils from activity impacted sites (12 sites) studied ranged between 0.2 to 254µg/g at these sites. The sum BaPeq at the sites ranged between 0.0 (a forest soil (k)) and 16.7 µg/g (a lubricating oil depot soil(c)). The MDI of each composite soil sample compared with that of food revealed that some of the individual PAH in samples from sites A (a dump site), C (a depot and loading point for used for black oil), F (a dump site), G (a petroleum depot), H (a roadside) and L (a car park) exceeded the recommended MDI threshold for food, indicating some risk associated with activities on these sites based on the ingestion estimate value. The Fed Organic Estimation Human Simulation Test (FOREhST) used to quantify bioaccessible PAHs in soils showed that not all the PAHs present in soils were bioaccessible. Re-evaluation of the risk based on bioaccessible PAHs showed that although PAHs were present and the amount of bioaccessible PAH based on oral risk assessment will not trigger cancers as depicted in the estimated theoretical cancer risk (ER) 9.47 x 10-10 – 4.08 x 10-07 for an adult. PAHs are lipophic as a result; bio accumulates in plants and other living organisms reaching levels that cause toxicological effects. It is important to reduce exposures to sites with high levels of PAHs. The study of PAH uptake by plant as a risk assessment approach, showed that the uptake of PAHs by plants was directly proportional to the concentration of PAHs in soils. The amount of PAHs in plants grown on contaminated sites compared to the control site revealed increased concentrations with amounts in the roots being generally higher than in stems followed by leaves for all the plants. Telfairia occidentale (Ugwu), consistently grew on all the soils which include the contaminated soils while shoko only grew on least contaminated soils .