Pesticides study wake up call for food safety regulators

Tuesday, January 26th, 2021 00:00 | By
Pest control. Photo/Courtesy

Dr Peterson Warutere 

The United Nations Population Division estimates that by 2050, there will be 9.7 billion people on earth. 

To keep pace with population growth, Food and Agriculture Organisation (FAO) estimates that in developing countries, 80 per cent of necessary increases in food production is projected to come from increases in yields and number of times per year crops can be grown on the same land.

Only 20 per cent of new food production is expected from expansion of farming land. 

About 20-40 per cent of global potential crop production is lost annually because of pests and diseases.

To curb this, there is extensive use of pesticides,.  Globally, a total of over two million tonnes of more than a 1,000 different types of pesticides are used annually. In Kenya, they have been used for over 90 years with 17,803 tonnes imported in 2018.  

Kenyatta University (KU) recently carried out a study on safety status of tomatoes grown and consumed in Kirinyaga county, the second leading tomato producing county in the country.

Records show Kenya contributes 340,000 tonnes to the 177 million global annual tomatoes production.

In addition, tomato is the second leading vegetable in Kenya in terms of value after potato with its open field production accounting for 95 per cent of total produce. 

 The study sought to determine pesticide residue levels in tomatoes grown in open fields, in greenhouses and levels in the market and at consumer level.

Randomly sampled tomato specimens were analysed at the KEPHIS Laboratory using the QuEChERs Multi-Residue method.

QuEChERS stands for Quick, Easy, Cheap, Effective, Rugged and Safe and was developed by the Codex Alimentarius Commission (CAC), the intergovernmental organisation that sets food standards, to establish Maximum Residue Limits (MRLs) expressed in mg/kg body weight for pesticides in food. 

 Of all samples, 56 per cent had pesticide residues above detection limit of 0.001mg/kg which included all samples from greenhouses, 40 per cent of those in open fields and 60 per cent at consumers’ tables.

About 43 per cent of samples had one pesticide residue, 8.6 per cent had two pesticide residues, while 5.7 per cent had three pesticide residues. 

 Compared with CAC MRLs, about 30 per cent of samples from greenhouses had pesticides residue levels significantly above the recommended limits.

These included fungicides Azoxystrobin, Carbendazim and Difenoconazole and insecticides Malathion and Acetamiprid. Samples collected from open field farms had significant levels of Acetamiprid, Carbendazim and Malathion while 40 per cent of samples at market levels had significant Acephate levels above recommended limits. Carbendazim levels at consumer level was also above limits.  

Of importance is degree of toxicity of active reagents of pesticides. Simranjeet et al (2016) in their study on toxicity, monitoring and biodegradation of  Carbendazim found it causes embryotoxicity, apoptosis, teratogenicity, infertility, hepatocellular dysfunction, endocrine-disrupting effects, disruption of haematological functions, mitotic spindle abnormalities, mutagenic and aneugenic effect.  

While the KU study showed about 42 per cent of  tomato farmers had been trained on safe use of pesticides, errors such as application of multiple pesticides with similar active ingredients particularly after severe pest attack were observed. This illustrates information gap affecting majority of farmers.  

It is, therefore, prudent for the government and regulatory bodies to heed WHO’s call to ban pesticides that are toxic to humans and that remain for the longest time in the environment and  to protect public health by setting maximum limits for pesticide residues in food and water. — The writer is occupational health and safety expert and lecturer at Kenyatta University [email protected]

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