Paul Brent, Canberra, Australia
1. Introduction
For Australia and New Zealand (and many other countries), emerging chemical contamination issues in food that have had a significant impact for government, consumers and industry alike include:
- chloropropanols in soy and oyster sauces and other foods,
- acrylamide in food,
- semicarbazide in lids of food containing glass jars,
- nitrofurans in honey and prawns, and
- mercury in fish.
These contaminant issues have required significant effort on the part of risk assessors, risk managers and risk communicators from government and industry, so that real or perceived health risks from contaminants in food are reduced thus avoiding food safety problems, consumer uncertainty, overly cautious regulation and trade disruption/WTO disputes.
Recently the management of low levels of residues of veterinary drugs (such as nitrofurans and chloramphenicol) without an ADI/MRL has become a major issue for government regulatory agencies. This paper describes the processes by which MRLs are developed in Australia, outlines some possible strategies to address the issue of low levels of chemicals without ADIs/MRLs and presents two case studies on risk management of recent emerging chemicals issues in Australia for consideration.
1.1. The Role of Food Standards Australia New Zealand (FSANZ)
FSANZ's role is to protect the health and safety of people in Australia and New Zealand through the maintenance of a safe food supply. FSANZ is a partnership between ten Governments: the Commonwealth; Australian States and Territories; and New Zealand. It is a statutory authority under Commonwealth law and is an independent, expert body.
FSANZ is responsible for developing, varying and reviewing standards and for developing codes of conduct with industry for food available in Australia and New Zealand covering labelling, composition and contaminants. In Australia, FSANZ also develops food standards for food safety, maximum residue limits (MRLs), primary production and processing and a range of other functions including the coordination of national food surveillance and recall systems, conducting research and assessing policies about imported food.
2. How Maximum Residue Limits are Developed in Australia
2.1. The Use of Agricultural and Veterinary Chemicals
In Australia, the Australian Pesticide and Veterinary Medicine Authority (APVMA) is responsible for registering agricultural and veterinary chemical products, granting permits for use of chemical products and regulating the sale of agricultural and veterinary chemical products. Following the sale of these products, the use of the chemicals is then regulated by State and Territory 'control of use' legislation.
Before registering such a product, APVMA must be satisfied that the use of the product will not result in residues that would result in an undue risk to the safety of people, including people using anything containing its residues.
2.2. Maximum Residue Limits
The MRL is the highest concentration of a chemical residue that is legally permitted or accepted in a food. The MRL does not indicate the amount of chemical that is always present in a treated food but it does indicate the highest residue that could possibly result from the registered conditions of use. The concentration is expressed in milligrams per kilogram (mg/kg) of the food.
MRLs assist in indicating whether an agricultural or veterinary chemical product has been used according to its registered use and if the MRL is exceeded, then this indicates a likely misuse of the chemical product. MRLs are also used as standards for the international trade in food. In addition, MRLs, while not direct public health limits, act to protect public health and safety by minimising residues in food consistent with the effective control of pests and diseases.
When a chemical product is registered for use or a permit for use granted, APVMA includes MRLs in its APVMA MRL Standard. These MRLs are then adopted into control of use legislation in some jurisdictions and assist States and Territories in regulating the use of agricultural and veterinary chemicals.
Dietary Exposure
Before registering a chemical product, the APVMA determines the residues of the chemical that will remain in treated food and assesses how much of this chemical a person may be exposed to in the diet. The APVMA determines the MRLs for agricultural and veterinary chemical products after a comprehensive evaluation of scientific studies on chemistry, metabolism, analytical methods and residue trials. If the APVMA is satisfied that the residues will not represent an undue risk to human health then the APVMA registers the chemical product and provides the MRL to FSANZ for consideration.
As part of the Australian registration process, scientists in the Therapeutic Goods Administration (TGA) review results from a wide range of experiments to evaluate the toxicology of a chemical. These experiments investigate the effects of the chemical to determine the level that can be safely consumed over a lifetime (i.e. the ADI[25]) and where necessary, the level that could safely be consumed from a single meal or during a single day (i.e. acute reference dose).
Following receipt of the MRLs from the APVMA, FSANZ checks the APVMA dietary exposure assessment to ensure that the residues do not represent an unacceptable risk to public health and safety. We do this by ensuring that estimated dietary exposure to the residues of a chemical does not exceed the ADI.
Recently, FSANZ and the APVMA have agreed to assess the acute exposure to agricultural and veterinary chemicals. Acute exposure assessments measure the potential adverse effects of consuming a food containing a pesticide at a single meal or during a single day. i.e. the immediate effects that a chemical residue in a food might cause.
Monitoring of Pesticide Residues after Registration
After registration, considerable resources are used to monitor the use of agricultural and veterinary chemicals. State, Territory and Commonwealth Governments all have agencies to monitor residues in agricultural produce to ensure that we are not exposed to unsafe levels of residues. FSANZ conducts a total diet survey every two years to estimate the level of dietary exposure for Australian consumers to a range of pesticide residues. Further information on the survey is available on the web site. In addition to these surveys, industry carries out many tests as part of commercial arrangements. The agencies involved in monitoring pesticide residues are listed in attachment 2.
Extensive monitoring data has shown that residues, if detected, are hardly ever present at concentrations even approaching the MRL. However, MRLs do indicate the highest residue that could result from the registered conditions of use and so residues at the MRL are possible.
2.3. Maximum Residue Limit Applications
After registering the agricultural or veterinary chemical products, based on their scientific evaluations, APVMA makes applications to FSANZ to adopt the MRLs in Standard 1.4.2 of the Code. FSANZ reviews the information provided by APVMA and validates whether the dietary exposure is within agreed safety limits.
If satisfied that the residues do not represent an unacceptable risk to public health and safety and subject to adequate resolution of any issues raised during public consultation, FSANZ will then agree to adopt the proposed MRLs into Standard 1.4.2 of the Code.
FSANZ then notifies the Australia and New Zealand Food Regulation Ministerial Council (Ministerial Council) of the proposed adoption of the variation into the Code. If the Ministerial Council does not request FSANZ to review its decision, the MRLs are automatically adopted by reference under the food laws of the Australian States and Territories, after gazettal by FSANZ.
The inclusion of the MRLs in the Code has the effect of allowing legally treated produce to be legally sold, provided that the residues in the treated produce do not exceed the MRL. Changes to Australian MRLs reflect the changing patterns of agricultural and veterinary chemicals available to farmers. These changes include both the development of new products, and the withdrawal of older products following review.
When FSANZ considers the issues associated with MRLs it should be noted that MRLs and amendments to MRLs by FSANZ do not permit or prohibit the use of agricultural and veterinary chemicals. The approvals for the use of agricultural and veterinary chemicals and the control of the use of agricultural and veterinary chemicals are regulated by other Commonwealth, State and Territory legislation.
In summary, the MRLs in APVMA's MRL Standard are used in some jurisdictions to assist in regulating the use of agricultural and veterinary chemical products under State and Territory 'control-of-use' legislation. Whereas the MRLs in the Code apply in relation to the sale of food under State and Territory food legislation and the inspection of imported foods by the Australian Quarantine and Inspection Service.
3. Future Strategies to Address Low Level Chemicals Without ADI/MRLs.
Given recent situations arising from the detection of low levels of non-complying residues of chloramphenicol and nitrofurans, FSANZ believes it is appropriate to consider the existing approach that is used in respect of regulating residues of agricultural and veterinary chemicals in food in Australia (note that New Zealand has separate regulations for MRLs from Australia).
3.1. Existing Approach
Currently, residues of agricultural and veterinary chemicals are prohibited in food unless they comply with specific limits stipulated in the Australia New Zealand Food Standards Code. This approach ensures that residues of these substances are kept as low as possible consistent with the domestic use of chemical products to control pests and diseases of plants and animals. It also ensures that only those residues that have been assessed as 'safe' by regulatory authorities in Australia are permitted in food. This approach is similar to that used by other countries such as the United States of America.
However, this approach does create some difficulties for enforcement agencies where low-level non-complying residues are found in food and these residues have been assessed as posing a low risk to public health safety. In these circumstances, the food does not comply and breaches food legislation but the low public health significance means that enforcement agencies have difficulty in mandating recalls, and are essentially forced into taking regulatory action and expending the resources of enforcement agencies where the public health risk is low. There are also the difficulties of managing perceptions around a food not being 'legal' yet of low risk to public health and safety.
This is further exacerbated by the fact that the limits in the Code relate to the domestic use of chemical products rather than the 'global' use of chemical products. Given that other countries have different pests and diseases, this means that food may be imported into Australia that contains residues that do not comply with the limits in the Code, even though these foods may be safe for consumption.
Technology has enabled analysts to achieve lower limits of reporting and it could be argued that the current approach of 'no detectable residues' results in a situation where the analytical capability determines the policy for regulating residues rather than the public health implications.
3.2. Alternative Options
Australia is attempting to adopt a more proactive approach by considering how the present processes could be altered to improve the management of MRLs setting and specifically the issue of low levels of chemical residues without ADIs/MRLs. Some of the options under consideration in Australia at the moment for managing low levels of residues of agricultural and veterinary chemicals, although there are several possible permutations within these options, might include:
- greater harmonisation of administrative processes between agencies responsible for MRLs setting in Australia
- removal of the prohibition of residues of agricultural and veterinary chemicals in food and reliance on a 'case by case' assessment of the public health implications of low-level residues;
- retention of the prohibition but with the inclusion of general 'default' levels and/or the inclusion/recognition of other MRLs;
- retain the current approach in the Code but institute stricter requirements in State and Territory food legislation.
4. Case studies
Two case studies are discussed below, based on Australian experiences, to illustrate recent examples of emerging chemicals and contaminants issues and how these have impacted on the food supply.
4.1. Case Study 1: Contaminant: Semicarbazide
The Issue: Semicarbazide has been recently found in Europe in some plastic sealing gaskets used in lids of foods packaged in glass jars and bottles. Semicarbazide is a chemical which carries some potential for causing cancer in animals. It is believed that this substance may migrate from the plastic sealing gaskets used in the lids of glass food containing jars, however only very small quantities of semicarbazide may reach the food. The particular concern with semicarbazide was that the glass jars are often used to package baby foods.
There are three types of sealing gaskets used in the lids of glass jars: a soft foamy type, a semi-foamy type and a hard type. These gaskets have been in use around the world for at least 30 years. Semicarbazide may be a by-product of chemicals used to manufacture the soft foamy and semi foamy types of gasket. The hard type of gasket is not linked to the possible occurrence of semicarbazide.
Risk Analysis: The European Food Safety Agency (EFSA), first issued advice on 28 July 2003, reporting that safety data available on semicarbazide is at present very limited. The available data suggests a potential for carcinogenicity in animals, but at much higher levels than reportedly found in foods. There is no evidence that semicarbazide causes cancer in humans and all the available toxicological data are insufficient to draw any firm conclusions. Studies have been commissioned by the EFSA in order to clarify some of the gaps in the available data.
EFSA released a further statement on 15 October 2003 stating that "The risk to consumers resulting from the possible presence of semicarbazide in foods - if any - is judged to be very small, not only for adults but also for infants. Although there are uncertainties in the risk assessment due to lack of full data at present, these relate only to how to assess what is considered to be a very small risk." Their full report can be found on http://www.efsa.eu.int/. The European Commission also stated in January 2004 that it will require manufacturers to stop using semicarbazide in sealants by 2005.
Risk Management: Food Standards Australia New Zealand (FSANZ) believes that there is no evidence to suggest a food safety concern for any consumers, including infants, from the chemical semicarbazide. No immediate action on the part of consumers or retailers is recommended regarding the occurrence of semicarbazide in any foods, including baby foods, packed in glass jars and bottles. In the meantime, FSANZ advice to consumers continues to be that there is not a food safety risk and that we should continue to eat a balanced diet including food packaged in glass containers.
FSANZ is liaising with food regulatory authorities around the world to share the latest information on semicarbazide. However, FSANZ considers that even low levels of semicarbazide are not desirable in the food supply. FSANZ has met with the food industry and manufacturers of these sealants who have informed us that they are developing alternative methods of sealing glass jars. These new sealants will take some time to be developed and tested by industry before being used. This is to ensure that they are as effective as the previous type as sealant in preventing food from being contaminated by food poisoning bacteria.
4.2. Case Study 2: Veterinary Chemical: Residues of nitrofurans in prawns
The Issue: Nitrofurans are synthetic broad-spectrum antimicrobial agents used in some countries in human and veterinary medicine. There are 4 main nitrofuran chemicals referred to in the scientific literature, namely, furazolidone, furaltadone, nitrofurantoine and nitrofurazone.
In 1993, JECFA withdrew the health standard (i.e. acceptable daily intake) for these nitrofurans due to the incomplete nature of the toxicological database and concerns about carcinogenicity in animal studies. As a result, many countries, including Australia, subsequently restricted, or prohibited, the use of nitrofurans in food-producing animals and subsequently detectable residues in food products were not permitted.
In October 2003, data became available indicating that very low levels of a furazolidone metabolite, 3-amino-oxazolidinone, had been found in certain imported prawns. Where residues had been detected, they were only at a few parts per billion (µg/kg). However, in the absence of a specific maximum residue level (MRL), these residues were not permitted.
Risk Analysis: As a result of these test findings, FSANZ undertook a risk assessment to establish the level of food safety risk to consumers from the levels of residue being detected in prawns. The risk assessment was undertaken to help inform enforcement agencies as to whether any risk managements actions should be taken to protect consumer health, such as testing of prawns and/or recalls of batches of prawns containing detectable residues. The dietary exposure assessment component of the risk assessment utilised the residue concentrations found in an industry survey, and the hazard identification and characterisation was based on a re-evaluation of the data summarised in the JECFA monographs.
Risk Management/Risk Communication: The risk assessment indicated that the risk arising from these trace residues in prawns was very low and that the prawns were safe to eat. It was not considered necessary to recall prawns that had entered into distribution within Australia. However, given that these residues were not compliant with the Food Standards Code, the enforcement authorities were advised to introduce import testing of prawns for nitrofurans. A relatively low frequency of testing has been implemented, commensurate with the level of food safety risk to the consumer.
The issue of nitrofuran residues in imported prawns has received considerable media attention within Australia and government agencies have stressed that these prawns are safe to eat. However, the paucity of toxicological data and the absence of an acceptable daily intake posed a particular challenge to the risk assessment. These residues had been detected in other countries but Australia was unable to confirm their presence until a testing methodology was established. This also made the communication of the level of risk to the community more difficult, particularly in the light of sensational media reporting. FSANZ plans to publish its risk assessment on its website.
5. Conclusion
The issue of regulatory management of low levels of chemicals without ADIs/MRLs in food continues to be a problem for government, industry and consumers. Work needs to continue to harmonise as much as possible the impact of improved analytical methods, risk assessment issues, the regulatory frameworks already developed or under development within each country and the current international regulatory framework
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[25] Acceptable Daily Intake
(ADI) |
