LEVELS OF POLYCYCLIC AROMATIC HYDROCARBONS IN SOME BRANDS OF PASTAS IN NIGERIAN MARKET: AN ASSESSMENT OF POSSIBLE POTENTIAL HEALTH RISK

ABSTRACT

Concentrations of 16 priority polycyclic Aromatic Hydrocarbons (PAHs) were determined in 30 brands of Nigerian and imported pastas in Nigerian market. The pasta samples were categorised into (1) noodles (2) spaghetti and (3) macaroni. Analysis were performed by GC – MS after soxhlet extraction of the sample and clean up of the extract. The concentration of Σ16 PAHs in both the Nigerian and imported brands are in the range of 0.009 to 0.8 mgkg^-1 and 0.002 to 0.007 mgkg^-1 respectively. The Bap concentrations in 75% of the Nigerian samples were less than 0.001mgkg^-1 permissible limit specified for processed cereal based food while all the brands of imported samples were below the maximum limit. The concentrations of Σ8 carcinogenic PAHs in both the Nigerian and imported brands ranged from 0.001 to 0.01 mgkg^-1 and 0.001 to 0.004 mgkg^-1  respectively. The Margin of Exposure based on PAH8 as an indicator for the occurrence and effects of PAHs in food for generally exposed individuals were less than 10,000 in 25% and 0% for child and Adult scenarios respectively for Nigerian brands. For typically exposed individuals, it were 38% and 0% for child and Adult scenarios respectively. For imported brands of pastas, the MOE values were far higher than 10,000 for generally and typically exposed individuals in both child and Adult cases. The MOE values indicate serious concern particularly for children who are consumers of Nigerian brands. 

CHAPTER ONE

BACKGROUND

1.1    INTRODUCTION

The introduction and distribution of man-made compounds or excessive amount of natural compounds have created avenue to understanding the effects of polycyclic aromatic hydrocarbons on humans and the environment. It is therefore, necessary to study the effects on individuals to population, communities and environments. The contamination of food by chemical hazards is a worldwide public health concern. Among organic contaminants, polycyclic aromatic hydrocarbons (PAHs) represent an important class of food contaminants.¹

Food can be contaminated from environmental source, industrial food processing and certain home food preparation.^{2 – 4}  Humans are exposed to PAHs by various pathways. For non-smokers, the major route of exposure is consumption of  food and  it contributes to more than 90% of total PAHs exposures  of the general pollution in various countries.^{5 – 7} Food contamination may also occur during periods of atmospheric pollution in which PAHs are deposited on seeds, fruits or vegetables, which are then consumed.^{7 – 9}  Many studies have shown that cereals, vegetables¹⁰, oil and fat^{11 – 12} are the main contributors to the ingestion of PAHs. However, grilled or smoked fishes and meats show a relatively low contribution, except in specific cases or due to socio- cultural reasons that cause these foods to occupy a prominent place in the diet.^{7, 13- 14}

Over the years, different sources of PAH contamination of food have been found. Food items and products could be contaminated by soils, polluted air and water.¹⁵ Some aquatic food products, such as fish, can be exposed to PAHs present in water and sediments and the PAH content greatly depend on the ability of the aquatic organisms to metabolize them.¹⁶

Furthermore, in the food processing industry, food additives such as smoke flavouring products  (SFP), lubricants, solvents, propellants, glazing agents and protective coating contribute to contamination of food items by PAHs.¹⁷

The occurrence of PAHs in human foods reflects the conditions of the environment and consequences of some thermal treatments that are used during the preparation and manufacture of foods.⁶⁶  The amounts and types of polycyclic aromatic hydrocarbon compounds generated during thermal processing of foods depend on the temperature, oxygen availability, fuel type used, treatment duration, fat content and distance from the energy source.⁵⁷  In areas remote from urban or industrial activities, the levels of PAHs found in unprocessed foods reflect the background contamination, which originates from long distance airborne transportation of contaminated particles and natural emission from volcanoes and forest fires. In the neighborhood of industrial areas or along highways, the contamination of vegetation can be ten-fold higher than in rural areas.¹⁸

In general, PAHs are not present individually but in mixtures. Sixteen PAHs that have be extensively monitored are the compounds included in the United States Environmental Protection Agency (USEPA) list of priority organic pollutants.¹⁹  The 16 compounds are given in Table 1 along with their abbreviation, molecular weight, Chemical abstract service (CAS) number and structure. Of these 16 PAHs, Benzo [a] Pyrene (BaP) is probably the most studied and has been widely used in environmental analysis as marker for the entire PAH content.⁵

Different approaches have been proposed for the assessment of the risk of PAH mixtures in human foods which include the use of Benzo [a] Pyrene as a maker, the toxic equivalency factor (TEF), margin of exposure (MOE).^{2, 20}  These approaches have been evaluated and the TEF was adjudged not scientifically valid because of lack of data on the oral carcinogenicity studies on the individual PAHs, their mode of actions and evidence of poor productivity of the carcinogenic potency of PAH mixture based on the current proposed TEF values.^{2, 5, 15}   In 2008, the CONTAM Panel of EFSA concluded that the use of  BaP as indicator of occurrence and effects of PAHs in food is not suitable and suggested that the eight higher molecular weight PAHs (PAH 8): Benz[a] anthracene, Chrysene, Benzo[a] Pyrene, Benzo [b] fluoranthene, Benzo [k] fluoranthene, Dibenz [a,h] anthracene, Benzo [g,h,i] perylene and indeno [1,2,3-c,d] pyrene and a sub groups of four PAHs (PAH 4: Benz[a] anthracene, Benzo[a] Pyrene, Benzo[b] fluoranthene, and Chrysene) are the most suitable indicators of occurrence and effects of PAHs in food. It was also suggested that the margin of exposure (MOE) approach should be used for assessment of risk exposure.²

Table 1: Polycyclic aromatic hydrocarbons considered in the present study.

Abbr: Abbreviation, Mw: Molecular weight, CAS: Chemical Abstract society service number

1.2       GENERAL OBJECTIVE