Pesticide Residues in Milk and Its Possible Mitigation

By Dr. Sadiya Sajad

Rampant globalization, urbanization, overpopulation, global warming and climate change is posing serious threats to the agricultural sustainability and the food producing systems ought to be safeguarded at any cost for the future generations. Use of pesticides across the globe is one such step towards it as their use increases the crop yield and fights against various crop diseases, however, the higher efficiency and lower cost of pesticides leads to its simultaneous over-utilization. The synthetic pesticides are classified into four major classes, namely organochlorine pesticides (OC), organophosphorus pesticides (OP), carbamate pesticides (CB), and pyrethroid pesticides (PY). Organochlorine pesticides are usually used as insecticides, herbicides and fungicides against a broad range of insects and fungi in the agriculture sector. They have been detected in milk and dairy products over the past three decades, particularly in the form of Dichlorodiphenyltrichloroethane (DDT) and Hexachlorocychlohexane (HCH). These were banned in different time periods in different countries because of the harmful effects and their persistence within the environment. Organophosphorus pesticides have been used increasingly in agriculture after banning or restricting the use of organochlorines. Organophosphorus pesticides including malathion, dimethoate, coumaphos, dichlorvos and parathion methyl; are highly toxic to mammals and are considered as mutagens, carcinogens and teratogenic substances. Carbamates are organic pesticides that include carbaryl, carbofuran and aldicarb. Their degradation is easy in the natural environment. Synthetic-pyrethroid including permethrin, cypermethrin, deltamethrin, cyhalothrin and bifenthrin can affect brain dopaminergic and serotonergic systems and provoke neurobehavioral changes in Wistar rats. They can also affect learning, memory-related characteristics, and reduce the homing ability of Apis mellifera bee or inhibit the acetylcholinesterase at the synaptic junction of the fish Odontesthes bonariensis, which provoke lethal effects. 

The inclusion of the pesticide residues in the food chain is seen when animals consume water, grass or feed and fodder contaminated with pesticide residues; also whenever the pesticides are sprayed over the animals in the barns inorder to relieve them from the ectoparasites and vector borne-diseases. After feeding and ingestion, these residues inevitably assimilate into the animal body systems. Pesticide bio-concentration and bio-accumulation in animal tissues is possible to reach the toxic levels even if the exposure was low. Once ingested, lipophilic pesticides are absorbed from the intestines into the systematic circulation. High lipid solubility of pesticides and their metabolites tend to accumulate in high fat content tissues such as adipose tissue, brain, liver, kidney and subsequently translocated and excreted through milk or other excrements.  Additionally, an increasing amount of pesticides and their residues are entering into our environment, which is undoubtedly hazardous to human, animals and ecosystems health. Humans-beings being on the top of tropic level or in the food chain, are bigger consumers of pesticides. Livestock products: meat, fish, eggs and especially dairy products are main source of OCPs and OPPs intake in general public.

Most pesticide residues in milk being fat-soluble can affect human health at low doses, even though they are considered as not harmful by health authorities. Many pesticides and their residues that enter the human body through the food chains are recognized as stimulants, causative agents or primarily contributory factors in several serious human diseases such as disruption of the endocrine system, neurological and immune system disorders, sterility, different cancer types (breast, lung, cervix, and prostate), heart diseases, Alzheimer’s and Parkinsonism. Children and older people being more prone as this specific age group is more sensitive to several pesticides due to their high intake of milk and dairy products in relation to their body weight and to the immaturity of their defence systems against chemical stressors.  

European Commission has established Maximum Residue Levels (MRL) as a measure to evaluate the maximum residue levels of pesticides in or on food and feed of plant and animal origin. The MRLs for milk and dairy products is ranged between 0.8 and 2000 μg/kg for the European Commission or range between 0.4 and 1000 μg/kg according to FAO and WHO. Moreover, a specific regulation for food consumed by children, and infants have been established by the European Commission (2013) to restrict the use of pesticides in infant formulas as much as possible. The chemical pesticides, however, cannot be outrightly banned but a risk benefit assessment should be performed before suggesting that a particular chemical treatment is to be stopped due to the risk of contaminating the food chain. For example: Organochlorine pesticides, particularly dichlorordiphenyl trichloroethane (DDT) and hexachlorocyclohexane (HCH), were the highly used pesticides in Punjab region of India until restrictions on their use were enacted in the late 1990s. Nevertheless, a substantial amount of DDT and c-HCH (lindane) chemicals are being permitted for use in the malaria-control program and in agriculture, respectively. 

The development and use of mitigation strategies should be a priority which includes:-Standardizing the quantity of pesticides to be used inorder to  reduce the indiscriminate pesticide application; training farmers’ the correct method of applying pesticides; stringent standards for the application of pesticides; need for continuous monitoring of pesticide residues in milk and its products; to introduce non-chemical pest control alternatives such as ladybirds and parasitoid wasps; introducing bio-pesticides which involves micro-organisms like bacteria and fungus (the most utilized microbial pesticides are strains of Bacillus thuringiensis that produces a mix of proteins capable of killing several related species of insect larvae).  

• The author is working as Assistant Professor in the Division of LPT, MRCVS & RC (affiliated to LUVAS, Hisar, Haryana). Previously worked as Contractual Lecturer in the Division of LPT, FVSc & AH, SKUAST-K.

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