MICROBIAL LOAD AND HEAVY METAL LEVELS IN SOME VEGETABLES SOLD IN SELECTED MARKETS WITHIN IBADAN METROPOLIS, NIGERIA

Abstract

Microbial and heavy metal contamination of vegetables compromises the quality and safety of vegetables consumed in Nigeria. Information on the assessment of microbial load and heavy metal level in vegetables sold in Ibadan markets will assist in selection of vegetables with less public health risk. The goal of this study was to assess the levels of heavy metal and microbial load of commonly consumed vegetables on sale in selected markets in lbadan Metropolis, Nigeria. A descriptive cross-sectional study and laboratory analysis were conducted. A total of 125 vegetable sellers in the major markets: Bodija: (58), Gate: (44) and Oje: (23) were interviewed. A pretested interviewer questionnaire was administered. The questionnaire included information on socio-demographic characteristics, hygiene practices and commonly sold vegetables. A six point practice scale was used to assess the hygiene practices. Practice scores of 0-3 and 4-6 were rated as poor and good hygiene respectively. Vegetable samples are collected from consenting sellers and were analysed for heavy metal concentration and microbial load in the morning (8-9am) and evening (4-5pm) for a period of 12 weeks. The heavy metals (Lead (Pb), Cadmium (Cd), Zinc (Zn), Nickel (Ni) and Copper (Cu)) and microbial load were determined using Atomic Absorption Spectrophotometer and polish standard procedure PN89/Z-04008/08 respectively. Data were analysed using descriptive statistics, t- test and ANOVA. Mean age of the respondents was 37.9±13.6 years and majority (61.2%) had good hygiene practices. Commonly sold vegetables were: Celosia argentea (Soko), Corchorus olitorius (Ewedu), Amaranthus viridis (Tete), Talimum triangulare (Water leaf) and Cucurbita maxima (Ugwu). Talimum had the highest mean Pb concentration (1.70±2.07mg/kg) and Lead in Cucurbita (0.43±0.35mg/kg) exceeded the WHO/FA0 standard (0.3mg/kg). Cadmium concentration Was highest in Talimum and Cucurbita (0.17±0.25mg/kg) and lowest in Amarathus (0.03±0.002mg/kg) and Celosia (0.02±0.01mg/kg) which was lower than the WHO/FAO standard (0.2mg/kg). Zinc concentration fell within the safe limit (99.4mg/kg) in Celosia (0.29±0.10mg/kg), Corchorus (0.28±0.27mg/kg), Amaranthus (0.19±0.18mg/kg), Talimum (0.04±0.02mg/kg) and Cucurbita (0.13±0.97mg/kg) Also, Nickel concentration fell within the safe limit (0.7mg/kg) in Celosia (0.08±0.11mg/kg), Corchorus (0.03±0.19mg/kg), Amaranthus (0.09±0.10mg/kg), Talinum (0.03±0.01mg/kg) and Cucurbita (0.03±0.01mg/kg) (p<0.05). Copper concentration in Talinum (0.22±0.14mg/kg) was the highest and exceeded the WHO/FAO standard (0.2mg/kg). Heavy metal concentration were higher in the evening samples for Pb (1.65±1.70mg/kg), Zn (0.25±0.22mg/kg) and Cu (0.20±0.17mg/kg), while that of Cd (0.51±0.96mg/kg) and Ni (0.51±0.86mg/kg) were higher in the morning samples (p<0.05). Coliform count was also found to be higher in the evening samples (9.8x10⁵±1.2x10⁶cfu/g). The predominantly isolated microorganisms were Staphylococcus sp, Escherichia coli and Aspergillus sp. Corchorus (7.27x10⁶cfu/g), Talinum (2.53 x10⁶cfu/g), Cucurbita (2.26 x10⁶cfu/g) had the highest total bacteria count, total coliform count and total fungal count respectively. Vegetables sold in Bodija, Gate and Oje markets were laden with heavy metals and characterised by presence of microorganisms of public health importance. Periodic assessment of microbial and heavy metal contamination of vegetables sold in markets by constituted authorities is recommended for promotion of food safety.