Pesticide residues in foodDr Nik Nor Ronaidi bin Nik Mahdi
Content• Introduction• Pesticide residue• Susceptible population• Principle of pesticides risk assessment• Health effect of pesticides• Prevention and control
Introduction• A pesticide is any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest. (US EPA)• Pests include insects, plant pathogens, weeds, molluscs, birds, mammals, fish, nematodes (roundworms), microbes and people that destroy property, spread or a vector for disease or cause a nuisance
Pesticides are often referred to according to the:1) Type of pest they control2) Derived from a common source or production method - chemical pesticides - biopesticides - antimicrobials - pest control devices
Chemical pesticides:• Organophosphate Pesticides - These pesticides affect the nervous system by disrupting the enzyme that regulates acetylcholine, a neurotransmitter. Most organophosphates are insecticides. However, they usually are not persistent in the environment. (e.g. parathion, malathion, and methyl parathion)• Carbamate Pesticides affect the nervous system by disupting an enzyme that regulates acetylcholine, a neurotransmitter. The enzyme effects are usually reversible. There are several subgroups within the carbamates. (e.g. Bendiocarb, Carbaryl, Methomyl, and Propoxur)• Organochlorine Insecticides were commonly used in the past, but many have been removed from the market due to their health and environmental effects and their persistence (e.g. DDT and chlordane).• Pyrethroid Pesticides were developed as a synthetic version of the naturally occurring pesticide pyrethrin, which is found in chrysanthemums. They have been modified to increase their stability in the environment. Some synthetic pyrethroids are toxic to the nervous system. (e.g. permethrin, resmethrin, and sumithrin )
• Biopesticides: – Pesticides derived from such natural materials as animals, plants, bacteria, and certain minerals. 1. Microbial pesticides consist of a microorganism (e.g. a bacterium, fungus, virus or protozoan) as the active ingredient. For example, there are fungi that control certain weeds, and kill specific insects. 2. Plant-Incorporated-Protectants (PIPs) are pesticidal substances that plants produce from genetic material that has been added to the plant. 3. Biochemical pesticides are naturally occurring substances that control pests by non-toxic mechanisms (e.g. insect sex pheromones that interfere with mating, and various scented plant extracts that attract insect pests to traps).
• National trends in the amount and composition of pesticides use: – For the year 2006, Malaysia experienced a 1% growth in pesticides usage. With increases in growth of 2% each for the chemical insecticides and fungicides compared the usage in 2005. – The composition of pesticides used in 2006 are 68% herbicides, 20% insecticides, 8% fungicides and 4% others and of these Class III and IV make up the most number of registered products. [The 25th Session Of The Asia And Pacific Plant Protection Commission (Apppc), 27- 31 August 2007, Beijing, China]
• Vegetable comprises about 15 % of the daily food intake of the Malaysian population (Ding et al., 1981).• Consumers generally demand for better quality vegetables. Quality vegetable to them means healthy, succulent and fresh looking vegetables with no visible rashes or holes caused by pests or diseases.• The use of agrochemicals including pesticides has been found to be the immediate and cheaper way to produce unblemished vegetables and increased farm productivity.• This practise has unfortunately created numerous problems associated with pesticide abuse such as accidental poisoning to man, upset of natural environment balance and toxic residues that are hazardous to health in the environment (Tay, E.B et al., 1984).
What are residues and why do they turn up in our food?• Pesticides may be used in a variety of different ways during the production of food: – used by farmers to control the growth of weeds, or prevent crop damage by insects, rodents and molds. – used on food crops after harvest to prolong their storage life. – used on animal farms to control insect pests• When a crop is treated with a pesticide, a very small amount of the pesticide, or its metabolites or degradation products, can remain in the crop until after it is harvested. This is known as the residue.
• Residues can arise from: – the use on a crop of legally allowed pesticides according to good agricultural practice – (leave smallest and acceptable amount of residue) – overuse of a pesticide, or use too close to harvest, of a legally permitted pesticide – illegal use of a pesticide that is not approved for that crop – incorrect use of pesticides after harvest, to reduce pest infestation in storage or in transit.
• Pesticide residues may be present in: – fresh or tinned fruit and vegetables, or – processed food and drink made from the crop (e.g. juice, bread or any other manufactured food or drink), or – fresh or processed animal products (if the animals have been fed on crop treated with pesticide).• Occasionally, residues may also result from environmental or other ‘indirect’ sources. (e.g. residues of old pesticides, such as DDT )
Do Processed Foods Have Less Pesticides Than Fresh Foods?• Generally, yes.• Reason: – Growers who have contracts with processors often don’t need to ensure that their foods are cosmetically perfect, and this allows them to omit some pesticide treatments, including some late-season insecticide applications. – Many processors, responding to consumer demand for foods with minimal pesticide residues, have contracts with growers that specifically limit pesticide applications. – Processing itself also often involves washing, peeling and cooking the food, steps that all tend to reduce pesticide residues.
What about organic food?“When present, residues in organic foods are likely to be at lower levels than those in non-organic foods.” (Baker et al.)
Common pesticide residue exceeding MRL in Sarawak from 2000 to 2006:• Organophosporus pesticide (OP) – 70%• Organochlorine pesticide – 15.3%• Synthetic pyrethroid – 11.6%• Ethylenebisdithiocarbamates (EBDCs) – 2.9% (Margaret Abat and Alvin Chai Lian Kuet, 2006)
(Margaret Abat and Alvin Chai Lian Kuet, 2006)
Susceptible population• The most vulnerable population - pregnant women, infants, and children: – children are much less able than adults to detoxify most pesticides – because they are growing and developing rapidly, processes that are vulnerable to disruption by toxic agents. – Since children’s bodies are smaller than adults’ bodies, they get greater doses of residues by consuming a given food than an adult would. – Children also eat fewer foods, and eat more of certain foods that tend to be relatively heavily contaminated with pesticides, than adults do.
Risk assessment1. Hazard identification: – The possible adverse health effects of the chemical are identified from toxicological studies.2. Hazard assessment: – The toxic effects and characterization of the biological response in terms of the dose ( i.e. the dose–response relationship, are considered and acceptable levels of dietary intake are derived).3. Exposure assessment: – Referred to as the ‘dietary intake estimate’, (i.e. the dietary exposure of residues resulting from the consumption of food and drinking water containing residues is estimated).4. Risk characterization: – the estimated dietary intake is compared with the acceptable levels of dietary intake or dose that were derived as part of the hazard assessment. In simple terms, if the dietary intake is less than this dose, then the risk is acceptable.
Health effects of pesticides• Birth Defects – A study in Minnesota found significantly higher rates of birth defects in children born to pesticide applicators and in regions of the state where chlorophenoxy herbicides and fungicides are widely used. (Garry, 1996) – In California, mothers living and working in agricultural areas with high pesticide use had a higher risk for giving birth to children with limb reduction defects. (Schwartz, 1988) – A study of pregnant women in Iowa and Michigan found that women exposed to multiple pesticides had an increased risk of giving birth to a child with cleft palate. (Gordon, 1981)
Health effects of pesticides• Neurological effects – Long term exposure can result in reduced IQ and learning disability, associated with permanent brain damage. – A study in Mexico shows that children living in area with high levels of pesticide exposure had less stamina, poorer eye-hand coordination, poorer memory and were less skilled in drawing figures. (Guillette, 1998) – The risk of developing Parkinsons disease is 70% greater in those exposed to even low levels of pesticides (Ascherio et al, 2006) – There are also concerns that long term exposures may increase the risk of dementia. (Baldi I et al, 2010)
Health effects of pesticides• Cancer – Associations have been found with: leukemia, lymphoma, brain, kidney, breast, prostate, pancreas, liver, lung, and skin cancers – Sheila Zahm and Mary Ward, summarized the studies of pesticides and childhood cancer and concluded that the following childhood cancers were linked to pesticide exposure: leukemia, neuroblastoma, Wilms tumor, soft- tissue sarcoma, Ewings sarcoma, non-Hodgkinss lymphoma, and cancers of the brain, colorectum and testes. (Zahm and Ward, 1998, Environmental Health Perspectives, vol. 106)
Health effects of pesticides• Fertility – A number of pesticides including dibromochlorophane and 2,4-D has been associated with impaired fertility in males. (Sheiner EK et al, 2003)
Prevention and control• Consumer’s education: – Choose foods frequently that have low TI values. – Choose foods with the highest TI values, such as peaches, less often. Eating these foods occasionally is unlikely to do much harm, but eating multiple servings in a short time probably should be avoided. – Look for organically grown food. – Remove the peel. Many pesticide residues are on the outside of a fruit. Removing the peel can dramatically lower pesticide exposure associated with these foods. – Choose processed foods more often, especially those for which TI are substantially lower than for fresh varieties of the same foods, such as canned peaches.
• Legislative approaches: – Pesticides Act 1974 which is implemented by a Pesticides Board, that has the Department of Agriculture (DOA) as its secretariat is the main Act that controls pesticides – the Food Act 1983 and The Food Regulations 1985 and (Amendment 1995) control pesticide residues in food and are enforced by the Ministry of Health; – Pesticides (Registration) Rules 1976 will ensure that the pesticides imported, manufactured, and sold in the country are of acceptable quality not causing unacceptable, adverse effects on human health and the environment.
– Monitoring residue: • Food Quality Control (FQC) unit and DOA – collect fresh produce at farm gate selling points and send it for residue testing • If exceed MRL, growers could be charged under Food Act and Regulations– Standards for residue: • National standards – Food Regulations 1985(Sixteenth schedule) • International standards – CODEX Alimentarius
• Malaysia continues to implement the Good Agriculture Practice as an effort to manage all hazards associated with agricultural production through such programs as the: – SALM (Malaysian Farm Certification Scheme For Good Agricultural Practice) – SOM (Organic Certification Scheme).
• Non-legislative and other approaches: – research into biopesticides by research institutions; – implementation and promotion of integrated pest management (IPM), such as the use of barn owls to control rats in paddy fields; – research into alternative pest control methods; – introduction of better pesticide application technology; and – promotion of alternative farming methods, including organic farming and hydroponics for the production of vegetables.
Factors on Persistent Occurrence of Contamination (Jinius Jipanin et al, 2001)• The DOA does not have any authority to take legal action against vegetable producers who do not comply with the standards• Immigrant workers with high turn over rate• The practice of profit-sharing in vegetable production between the workers and the land owners. – The land owners will provide all inputs, including PESTICIDES and marketting, while the workers are responsible to produce as much vegetable as possible. – The owners and workers work independently but with the common aim to maximise profit margins by whatever means. – This factor led to PESTICIDE ABUSE.• There is no proper control on the local vegetable marketing network. Practically anyone can grow vegetables and sell.• The current enforcement of the Food Act by the agency concern have been very sparse and the operation does not deter the potential pesticide abusers.
Factors on Persistent Occurrence of Contamination (Jinius Jipanin et al, 2001)• Farmer’s ignorant and misconduct: – Ignorant of the biological aspects of insects and microbial agents – Unable to choose the correct type of active ingredient (a.i) with regards to the pest problems. – Failed to follow directions on labels like dosage, application frequency and pre harvest interval (PHI). – Unaware of other pest control techniques – Wrongfully mixing a few active ingredients or “trademarks” to produce a “cocktail”• Most farmers prefer to use insectic ides in the organophosphorus (OP) group regardless of their toxicity and longer persistence in the environment because these chemicals are highly effective in knocking off the pests and are cheaper.