Human health risk assessment of dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) pesticide residues in fruits and vegetables in Nigeria

The residues of dichlorodiphenyltrichloroethanes (DDTs) and hexachlorocyclohexanes (HCHs) in forty-eight (48) composite fruit and vegetable samples (carrot, cucumber, tomato, and watermelon) were qualitatively and quantitatively determined using gas chromatography equipped with electron capture detector (GC-ECD). Safety indices such as the estimated average daily intake (EADI), cancer benchmark concentration (CBC), hazard quotient (HQ) and index (HI), and hazard ratio (HR) were also estimated. Results showed the predominance of HCH and its isomers in the fruits and vegetables as compared with the DDTs. The most predominant HCHs in all the fruits was α-HCH with mean concentrations of 2.704 ± 2.488 mg kg-1 (carrot), 1.536 ± 1.036 mg kg-1 (cucumber), 6.814 ± 2.967 mg kg-1 (tomato), and 9.241 ± 2.735 mg kg-1 (watermelon). The analysis showed that the levels of pesticide residues detected in 25 to 100% of the fruit and vegetable samples were above the UK/European Commission Maximum Residue Limits (MRLs). The non-carcinogenic health risk estimates showed that only α-HCH in tomatoes and watermelon had HQ > 1 which indicates the possibility of systemic health risk in children consumers. The carcinogenic health risk showed that only α-HCH and γ-HCH in children and α-HCH in adults had HR > 1 for tomato and watermelon which implies the possibility of carcinogenic health risk from its consumption. It is therefore paramount to institute a policy and regulatory framework for regular monitoring of pesticide residues in fruits and vegetables in Nigeria in order to ensure food safety for consumers and protect human health.

Occurrence and Human Health Risk of Dichlorodiphenyltrichloroethane (DDT) and Hexachlorocyclohexane (HCH) Pesticide Residues in Commonly Consumed Vegetables in Southwestern Nigeria

BACKGROUND

Fluted pumpkin (Telfairia occidentalis) and amaranth (Amaranthus spp.) are common leafy vegetables produced and consumed in southwestern Nigeria. These vegetables attract insect pests which are controlled by pesticides that may have adverse impacts on human health.

OBJECTIVES

To determine the levels of dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) pesticide residues in the two vegetables and evaluate the potential health risks associated with their consumption.

METHODS

The pesticide residue levels were quantitatively and qualitatively determined using a gas chromatograph coupled with electron capture detector. Health risk assessment were performed using estimated average daily intake and hazard indices for two weight categories: children (16.7 kg) and adults (60 kg).

RESULTS

The results showed that delta-HCH, DDT and methoxychlor were predominantly detected in the two vegetables from both farms and markets. In amaranth, the mean concentration of methoxychlor, DDT and delta-HCH were 4.590 ± 2.774 mg/kg (dry weight (dw)), 0.757 ± 0.457 mg/kg (dw) and 0.577 ± 0.390 mg/kg (dw), respectively, while fluted pumpkin levels were 6.223 ± 2.489 mg/kg dw (methoxychlor), 0.504 ± 0.056 mg/kg dw (delta-HCH) and 0.486 ± 0.123 mg/kg dw (DDT). The levels of HCH and DDT residues were generally above the United Kingdom/European Commission maximum residue limit. The analysis of health risk estimates for non-carcinogenic risk revealed that for both vegetables, the hazard quotient for p, p' DDT and methoxychlor was >1 for both children and adults. The health risk estimates for carcinogenic risk revealed that hazard indices values were >1 for children for both vegetables and alpha-HCH had a hazard index >1 for adults for amaranth. This means the residue exceeds acceptable standard and present potential risk to consumers of these vegetables.

CONCLUSIONS

The results obtained from the present study indicate that consumption of amaranth contaminated with alpha-HCH could pose a carcinogenic risk for adult consumers. The consumption of the two vegetables could pose both non-carcinogenic and carcinogenic health risks to children and adults. Therefore, there is need for strict enforcement of regulations on pesticide usage to minimize human health risks.

COMPETING INTERESTS

The authors declare no competing financial interests.

Dietary exposure assessment of organochlorine pesticides in two commonly grown leafy vegetables in South-western Nigeria

Organochlorine pesticides (OCPs) are persistent pesticides whose usage have been banned or restricted worldwide and the presence of its residues in vegetables could affect its nutritional quality as well cause adverse health effects. This study quantified the OCP residue levels in commonly grown and consumed vegetables and assessed the carcinogenic and non-carcinogenic health risks from the consumption of the contaminated vegetables. The OCP residues levels in the extract from the vegetables were determined using a Gas Chromatograph coupled with Electron Capture Detector (GC-ECD). Health risk estimates were analysed using Estimated Average Daily Intake (EADI), Hazard Index (HI), and Hazard Ratio (HR) for children (16.7 kg) and adults (60 kg) weight categories. The residue analysis indicated that amaranths had the highest mean concentration of endrin aldehyde (2.987 ± 0.391 mg kg^-1) and endosulfan sulfate (0.661 ± 0.280 mg kg^-1), while in fluted pumpkin, the highest mean concentrations were endrin aldehyde (3.491 ± 0.376 mg kg^-1) and endosulfan sulfate (2.775 ± 0.644 mg kg^-1). The percentage of the detected OCP residues above Maximum Residue Limits (MRLs) ranged from 25% to 100% for both vegetables. Non-carcinogenic health risk estimates for the children weight category showed that aldrin, dieldrin, endrin, endrin aldehyde, and heptachlor detected in both vegetables had HI > 1. While for adults, only aldrin, dieldrin, endrin, and endrin aldehyde revealed non-carcinogenic effect in both vegetables. Human risk estimations for the carcinogenic health effect for the two vegetables showed that aldrin and dieldrin could pose carcinogenic health risks to adult, while aldrin, dieldrin, heptachlor and heptachlor epoxide could pose carcinogenic health risks to children. The results revealed both non-carcinogenic and carcinogenic health risks for the consumers of the contaminated vegetables from the selected locations in South-western Nigeria.

Environmental monitoring of pesticide residues from farms at a neighbouring primary and pre-school in the Western Cape in South Africa

Concerns about pesticide drift from neighbouring vineyards affecting children attending school on a farm adjacent to an urban suburb of Cape Town, Western Cape in South Africa were investigated. The study involved a before-after design, measuring levels of environmental exposure before and during pesticide application activities on the neighbouring farms. Samples were collected in air, dust and grass cuttings at the preschool and primary school located on the farms during September-December in 2010 and tested for pesticides using multi-pesticide methods. Eleven different pesticides were detected in the various samples. Six of these chemicals (endosulfan, dimethomorph, penconazole, cyprodinil, boscalid and bromopropylate) were on the spraying schedules of the two farms neighbouring the schools and the timing and location of detection were generally consistent with farm application. Three pesticides detected (chlorpyrifos, cypermethrin, permethrin) are agents commonly used in household applications and one (pyriproxifen) is used in pet treatment agents. Kresoxim-methyl, the other pesticide detected, is likely to come from drift from other farms in the area. The concentration of pesticides was all lower than 0.1 μg/m(3) in air and 0.1 μg/kg in dust and grass apart from permethrin and cypermethrin. The findings confirm the presence of drift onto the school premises and concentrations found in this study were generally low in comparison to that detected in other studies. Regular monitoring to track the effectiveness of containment and mitigation measures that reduce drift is recommended.

Formulation of an effective mosquito-repellent topical product from lemongrass oil

Ointment and cream formulations of lemongrass oil in different classes of base and the oil in liquid paraffin solution have been evaluated for mosquito repellency in a topical application. Mosquito repellency was tested by determining the bite-deterrence of product samples applied on an experimental bird's skin against a 2-day starved culture of Aedes aegypti L. mosquitoes. The 1%v/v solution and 15%v/w cream and ointment preparations of the oil exhibited > or =50% repellency lasting 2-3 h, which may be attributed to citral, a major oil constituent. This activity was comparable to that of a commercial mosquito repellent. Base properties of the lemongrass oil formulations influenced their effectiveness. The oil demonstrated efficacy from the different bases in the order of hydrophilic base > emulsion base > oleaginous base.