Pesticide Residues in Raw Fruit and Vegetables and Fruit Juices
October 1996 December 1996
Report prepared by Andrew Rigg and Simon Christen
1.1 To determine the compliance of raw fruit and vegetables available in the ACT to the pesticide maximum residue limits (MRLs) specified in Food Standards Code (the Code).
1.2 To compare these results with results from previous years.
1.3 To determine the compliance of a number of fruit juices available in the ACT to the MRLs specified in the Code.
In Australia, there are over 270 different pesticides registered for use on fruit and vegetable crops, most of which are for the effective control of insect pests, fungal diseases and weeds. Pesticides are applied to control specific pests and diseases and are used according to good agricultural practice. This practice aims to ensure that minimal levels of residues (if any) are remaining on the harvested crop and that the food is safe to consume. The maximum residue limit (MRL) is the highest level of a pesticide permissible in food.
Pesticides can be broadly divided into a number of groups which relates to their functionality and structure. Examples of some groups and pesticides within the groups are:
- organochlorine pesticides, eg. DDT, dieldrin, chlordane, endosulfan;
- organophosphorus pesticides, eg. parathion, dimethoate, chlorpyrifos;
- synthetic pyrethroid insecticides, eg. deltamethrin, permethrin, fenvalerate;
- triazine herbicides, eg. simazine, atrazine;
- carbamate pesticides, eg. aldicarb, propoxur, carbofuran; and
- fungicides, eg. chlorothalonil, vinclozolin.
Most of the compounds that fall into the organochlorine category have been banned for food applications since the late 1970s or early 1980s. The cyclodienes (dieldrin, aldrin, chlordane and heptachlor) have been used as termiticides until 1992, but have been totally banned for use since then. Monitoring of foodstuffs on the Australian market through the Australian Market Basket Surveys have shown a continuous decline of organochlorine pesticide residues since the 1970s. This is reflected in an Australian study which found a progressive decline in human breast milk levels of organochlorine pesticides during the period 19741991 and in human adipose tissue levels during the period 19661991 (Stevens 1991).
One exception is the organochlorine endosulfan which is permitted for use on a wide range of fruit and vegetables, and grains. Endosulfan has advantages over many of the earlier organochlorines in that it is not persistent in the environment. For most fruit and vegetables, 50% of residues are lost in 37 days and in animals, endosulfan is metabolised and excreted in the urine (Kidd and James, 1991) and does not accumulate in milk, fat or muscle (ibid).
The organophosphorus pesticides are a very broad range of mainly insecticides and acaricides. They are cholinesterase inhibitors and as such can pose a significant occupational health and safety hazard for farm workers and can be fatal to small animals, birds and fish. There are a large number of pesticides in this group that are currently in use in Australia, covering a wide range of applications.
The synthetic pyrethroids are presently used extensively in Australia and have become the most significant class of agricultural insecticides since their introduction in the early 1980s. They have permitted applications in food crops (including fruits, vegetables and grains) as well as meat animals. Pyrethroids currently constitute approximately 25% of the world insecticide market for plant protection (Sherma and Cairns, 1993). As a class, they possess a number of significant advantages over most organophosphorus and organochlorine insecticides. These advantages include low toxicity to mammals and birds, rapid breakdown in the environment and rapid elimination from animals (Kidd and James, 1991).
Herbicides make up over half of the pesticides registered for use in Australia. They are generally less toxic to humans than insecticides. A number have been developed to inhibit metabolic pathways specific to plants (eg glyphosate inhibits the shikimic acid cycle in plants) and accordingly, have very low toxicity to animals.
The N-methylcarbamate group of pesticides are all derived from carbamic acid. As a class they are highly effective and have a broad spectrum of activity as insecticides, acaricides and nematicides. A number of the individual pesticides are in current usage in Australia. The carbamates are also cholinesterase inhibitors but, as a class, are less toxic than the organophosphorus insecticides. The carbamates generally degrade rapidly in the environment.
The fungicides are not a chemically related class of compounds, therefore, generalisations on toxicity are not applicable. Many fungicides have broad ranges of permissions for use on fruit and vegetables and a number are seen regularly in samples analysed by the ACT Government Analytical Laboratory (ACTGAL).
2.1 Pesticide residue screening
The pesticide residue program commenced in mid 1991 with the screening of raw fruit and vegetables. During the first two and a half year period, to December 1993, approximately six hundred samples were screened. Although residues were detected in slightly over 50% of the samples most of these were at levels well below the MRLs and only two samples were found to contain residues exceeding MRLs. During this time sixty five samples of "organic" raw fruit and vegetables were also screened and found to be virtually free of pesticide residues (as claimed).
During 1995 a further one hundred and fifty samples of raw fruit and vegetables were screened. In this survey, residues were detected in less than one third of the samples and only one sample was found to contain a residue which exceeded its MRL.
Samples of fruit and vegetables for this survey were collected from supermarkets, green grocers and fruit and vegetables markets in Canberra between January and June 1997. The samples were analysed for the organochlorine and organophosphorus insecticides, triazine herbicides and fungicides.
From April to June 1997 a separate survey on the levels of preservatives in fruit juices and drinks was conducted. A number of fruit juice samples from this survey were also analysed for pesticide residues and the results are included in this report
Standard A14 lists the maximum allowable limits (MRLs) for agricultural and veterinary chemical residues in food. This includes chemicals that have been permitted for use in the past and as a result of their stability, they may be detected in food from time to time (eg. organochlorine pesticides such as DDT and dieldrin).
Schedule 1 of the standard lists all the agricultural and veterinary chemical limits in particular food. The excerpt below lists the MRLs for the well known organophosphorus pesticide, chlorpyrifos, which is used in Australia to protect a large variety of agricultural commodities and to control termites. The standard also states that no residue must be detectable in foods not listed, so for example, chlorpyrifos residues are not to be detected in coconut.
Column 2 [MRL (mg/kg)]
|Vegetables [except asparagus, brassica vegetables, cassava, potato, tomato]||
The stated MRL applies for both raw and processed food. In foods which contain a proportion of ingredients with an applicable MRL, the MRL is not to be exceeded proportionately. For example, for an orange juice constituting 20% oranges, the MRL for chlorpyrifos in this food is 20% of 0.5 (Citrus Fruits 0.5 from table above) which is 0.1 mg/kg.
5.1.1 Raw fruit and vegetables
59 samples of raw fruit and vegetables were obtained, the majority being fruits as shown in Figure 1.
The samples can be further divided into their respective classes within the categories of fruits and vegetables, as shown in figures 2 and 3:
5.1.2 Fruit juices
There were 82 samples of fruit, vegetable and mixed juices (and fruit juice drinks) obtained. The samples were analysed principally for preservatives (See report entitled Preservatives in Fruit Juices and Fruit Juice Drinks, 1997) and 24 of these samples where analysed for organochlorine and organophosphorus insecticides, triazine herbicides and fungicides.
The samples included apple juice, orange juice, mango nectar, vegetable juice (constituting mainly celery and carrot), prune juice, pineapple juice, tropical juice, grape juice and guava nectar.
5.2 Pesticide Results
5.2.1 Raw fruit and vegetables
Figure 4 summaries the results of pesticides detected. 71% (42/59) had no pesticides, 25% (15/59) had one or more pesticides detected below the MRL, and 3% (2/59) failed to comply.
The samples which failed to comply are showed in the proceeding table:
* Endosulfan detected but passed MRL.
The sample of sugar bananas contained a residue of chlorpyrifos which marginally exceeded the MRL. Additionally, a star fruit sample was found to contain a low residue of chlorpyrifos which is not permitted. In this case it seems likely that the grower(s) used a pesticide that has no permitted application on star fruit.
For the other residues detected the average concentration found, expressed as a percentage of the particular MRL, was 26.7%. The minimum concentration detected expressed as a percentage of the MRL was 0.5%, whilst the maximum was 90%. These results are shown in figure 5.
The residues detected below the MRL included the organochlorine pesticides dicofol (an acaricide), endosulfan (a general purpose insecticides), and dieldrin(an insecticide normally used to control termites and previously permitted for agricultural use); the organophosphorus pesticides fenthion, chlorpyrifos and parathion; and the fungicides dicloran, iprodione and procymidone.
Of all the pesticides detected, endosulfan was detected the most often (5 samples), followed by iprodione (4), chlorpyrifos (3), fenthion (3), dicofol (3), dicloran (1), parathion (1), procymidone (1) and dieldrin (1).
5.2.2 Fruit juices
17% (4/24) of samples had detectable amounts of pesticides and all were below the respective MRL. The pesticides detected were: endosulfan sulphate (a breakdown product of the insecticide, endosulfan) in mango nectar; and iprodione, (a fungicide) in tropical juice, vegetable juice and apple & kiwi juice.
The results indicate that pesticide residues in fruit and vegetable, and for that matter in fruit juices, are within the MRLs as specified. Of the produce tested, the occurrence of pesticide residues was very limited, usually to less than 50% of the respective MRL.
Many testing agencies have noticed the trend towards less and less residues being found in our food supply (ANZFA, DPI&E). The likelihood of deliberate or accidental misuse of these chemicals is rare due to programs of better labelling and instructions for their use, support and service for the user to promote effective application of the chemical for their intended purpose and by having chemicals permissible to cover all situations as deemed necessary. The increasing cost of chemicals also means that unnecessary use would be expected to decline even further.
There is a minor problem (3%) with pesticides exceeding the MRL. This whole question of monitoring for pesticides in the ACT is under review by the Health Protection Service and a report will be made available shortly. The results suggest that monitoring of some chemicals should be continued, in particular for endosulfan, chlorpyrifos and possibly some of the fungicides.
71% of the samples had no detectable residues and 26% had residues below the MRL. The results indicate that pesticide residues pose a minimal health risk in these foods. Similar findings are also made from recent Market Basket Surveys coordinated by ANZFA. Of the two samples which exceeded a particular MRL, both were minor and are of little concern.
The consumer is entitled to expect foods to be free from harmful contaminants and this survey of fruit and vegetables and fruit juices available in the ACT suggest consumers expectations are being met.
As the pesticide testing performed by the Service is currently under review, the Service will not be analysing further samples until the review is complete and its recommendations implemented.
Food Act 1992 (ACT), reprint as at 31 January 1996.
Australia New Zealand Food Authority, Food Standards Code, incorporating amendments up to and including amendment no. 32, December 1996.
Australia New Zealand Food Authority, The 1994 Australian Market Basket Survey, Commonwealth of Australia, 1996.
International Programme on Chemical Safety, Carbamate Pesticides: A General Introduction, Environmental Health Criteria 64, World Health Organisation, 1986.
Department of Primary Industries and Energy, Chemical Residues in Food, Questions and Answers, Commonwealth of Australia, 1995.
Archer, Enymatic Methods,. In: G. Zweig, Analytical Methods for Pesticides, Plant Growth Regulators, and Food Additives, Volume 1, Principles, Methods and Applications, Academic Press, New York, 1963.
National Health & Medical Research Council, Cyclodiene Insecticide Use in Australia, AGPS, 1993.
Kidd and James, The Agrochemical Handbook, The Royal Society of Chemistry, 3rd edition, 1991.
Stevens, The concentration of organochlorine pesticides in the Western Australian population 19661991, Western Australia: Health Department, 1991.
World Health Organisation, International Program on Chemical Safety, EHC 104: Principles for the Toxicological Assessment of Pesticide Residues in Food, WHO, 1990.
This report could not have been possible without the work of Andrew Rigg in developing and validating the method and Margaret Woolcock for analysing the samples.