Annals of Occupational Hygiene Advance Access originally published online on September 23, 2006
Annals of Occupational Hygiene 2006 50(7):651-655; doi:10.1093/annhyg/mel060
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Pesticides and The Residential Bystander
TNO Senior Research Fellow in Occupational Toxicology TNO Chemistry, Zeist, The Netherlands
*Author to whom correspondence should be addressed. Tel: +31 30 6944913; fax: +31 30 6944707; e-mail: joop.vanhemmen{at}tno.nl
INTRODUCTION
Some time ago I stood on a public road in France watching a helicopter spraying pesticide on the fields of my father-in-law. The helicopter overshot and sprayed me as well. My father-in-law severely reprimanded the pilot and since then has no longer used aerial spraying, but the incident gave me an immediate experience of bystander exposure.
In Britain as in other countries there have been reports for several years of pesticide use near residential areas and alleged ill-health as a result. These reports have become stronger and stronger, and have led to a debate between various groups of activists/campaigners (or victims, as they consider themselves) and the government about the robustness of the regulatory risk assessment and management procedures for pesticides as they affect bystanders. A frequent element in the complaint is that the ‘victims’ could rarely prove that the health complaints were related to pesticides, because no information could be obtained on the relevant pesticide uses.
In an example, which shows many of these features, the New Zealand government arranged for spraying of some suburbs of Auckland with a biological control agent against a highly destructive moth accidentally imported from Australia. This led to many complaints of ill-health, an unofficial ‘people's enquiry’ presenting tearful witnesses on television, secrecy over the content of the spray because of a confidentiality agreement between the government and the US manufacturer, an independent enquiry which concluded that the spray was not injurious, a health effects enquiry (Aeraqua, 2005), and finally dissatisfied scepticism by victims and activists.
In Britain aerial spraying is very rare (CSL, 2001), and wholesale spraying of suburbs does not occur, but bystander exposure does happen, and complaints have contributed to a succession of official actions in recent years. First, Defra (the Department for Environment, Food and Rural Affairs) consulted on introduction of no-spray buffer zones between fields and residences, and measures to improve public access to information on pesticide use. The government accepted scientific advice not to introduce buffer zones, but affirmed that the top priority of the government was to ensure that the safety arrangements in place do protect the public, and noted that a fresh view on the basis of the risk assessment was timely because of the concerns of campaigners, who ‘have strong views on how crop spraying has affected their health’.
The Royal Commission on Environmental Pollution (RCEP) was, therefore, asked in June 2004 to examine the evidence on which the current regulatory system for residents and bystanders is based as well as the reasons for people's concerns.
The RCEP accepted the request and added to it that they would also consider the handling and communication of risk and uncertainty. Their report, ‘Crop Spraying and the Health of Residents and Bystanders’, was published in September 2005 (RCEP, 2005).
The ‘Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment’, and the ‘Committee on Carcinogenicity of Chemicals in Food, Consumer products and the Environment’ were asked by Defra and by the Advisory Committee on Pesticides to comment on health-related topics in the RCEP report, and they published a joint statement, which was critical of many aspects (COT/COM, 2006). The government response was published in July this year (DEFRA, 2006).
The European Commission is due to publish a Thematic Strategy on the Sustainable Use of Pesticides, which will include proposals for a new Directive. The position the UK government has now taken will undoubtedly guide its approach to these European Union discussions.
The approval process
To clarify the significance of the measures under discussion, it is necessary to understand the current procedures for regulating pesticides. Unlike most chemicals at present, pesticides have to be assessed and approved before they can be marketed. There are comparable procedures in most developed countries, but in the UK, the Pesticides Safety Directorate (an executive agency of Defra) provides the assessment of risks for agricultural pesticide uses. The independent ACP (Advisory Committee on Pesticides) advises the involved Ministers on all issues related to approvals of pesticides (grant, amend, or revoke).
In the approval process, likely exposure must be considered. The Annals has published many papers on this step, including a special supplement in 2001 based on an international workshop (van Hemmen and van der Jagt, 2001). The exposure considered under the current pesticide legislation is by inhalation and dermal contact, and (in special cases) oral uptake (e.g. through contact between skin and mouth). In the case of bystander and residential exposure, the exposure data are taken from dedicated field drift studies, where measurements have been made around treated (mainly open) fields during and after the treatment, which are considered worst cases. On the basis of a series of experiments under certain conditions of tractor speed, wind speed and concentration of the material applied to the field, the exposure data are evaluated and a so-called reasonable worst case approach is taken to estimate exposure data 
8 m from the edge of the tractor application boom. These data vary with the type of application: upwards (in tree crops with or without foliage) or downwards (in open fields). The numbers obtained in millilitres of spray liquid are then calculated and for the specific spray concentration the equivalent milligrams inhaled or received on the skin of the bystander (or resident) is determined, assuming that the bystander is unclothed (i.e. not protected by clothing). This exposure assessment approach has been developed in the European EUROPOEM project and the project report was published in 2002 (EUROPOEM, 2002). In the UK, the process has been adapted over time on the basis of new (improved) data and includes consideration of exposure to volatized active substance and exposure of children playing in gardens that have been contaminated with spray drift.
The possible health effects are studied using available evidence, which is largely based on experimental animal studies governed by the EU Directive 91/414/EEC. The toxicity tests that are required have to be done according to OECD test guidelines in Good Laboratory Practice compliance.
From the animal (and where available human) toxicological data, a value is derived, called the acceptable operator exposure limit (AOEL), which in the risk assessment is compared with the relevant expected exposure. The AOEL is derived from the no-observed adverse effect level (NOAEL) in the most sensitive animal for the most critical effect, allowing—in the general case—a factor of 10 for variability within species and a further factor of 10 for variability between species. In practice this means that the observed NOAEL in the most sensitive animal and for the most critical relevant adverse effect is divided by 10 x 10 to derive the AOEL. Additional factors may be added depending on the nature of the effect. In this approach account can be made of the frequency and duration of exposure by considering effects due to short exposure durations and low frequencies by choosing appropriate animal studies. For the operator who applies pesticides, exposure is usually sub-chronic or long-term and considered to occur daily, and this pattern forms the basis for the derivation of the AOEL. Although this assessment is not comprehensive from the point of view of mixtures of pesticides and possible individual susceptibility differences, the general view is that these factors are mostly, if not entirely, allowed for in the large safety factor of 100. If specific susceptibilities are known, they are considered in the process.
At the European level there have been extensive discussions as to whether for bystanders a different safety factor should be used. The current approach is that this is not necessary, since the factor 100 really applies to the general population (Boobis in BCPC, 2005, pp. 20, 21).
The RCEP report and its critics
The RCEP report covers several relevant issues, which may not all be of core interest for the readers of the Annals of Occupational Hygiene. They involve health issues, exposure assessment, legal liability and governance. The report has an elaborate introduction and a pretty large chapter with conclusions and recommendations. In this commentary, the attention will be focused on health issues and the exposure and risk assessment process.
On exposure assessment, the RCEP report challenges the ‘reasonable worst case’ approach summarized above, because they consider that the number of variables that govern the actual exposure to the bystander (and residents) is more complex than considered. The RCEP considered that the present approach is possibly not a worst case, since exposure is not only due to spray drift (the moving of the aerosols away from the spray boom) but also by volatilization of the active substance and the contamination of the premises (garden and garden crops) by the spray mist. Furthermore, the report challenges the large number of variables that are not accounted for by the experimental data used, such as height of the spray boom above the field and the nature of the crop treated (high or low, since the experimental data were mainly obtained while spraying arable land). The bystander/resident might even be closer to the spray boom than 8 m—spraying might be directly next to bystanders—which would then increase the level of exposure obtained. Tractor speeds might be higher than considered, and higher concentrations might be used in order to save time. The major criticism of the RCEP report on the procedures used in the UK (and for that matter in Europe) is that the description of the risk assessment (lack of transparency) does not account for these and other uncertainties in the risk assessment.
The standards applied to the toxicity data are very high for pesticides, and this is acknowledged by RCEP (2005). Nevertheless, RCEP focuses on putative health effects, and they specifically mention in this respect some results of epidemiological investigations and two multisystem syndromes: chronic fatigue syndrome (CFS) and multiple chemical sensitivity (MCS). These two conditions—if they are accepted as real—relate to increased susceptibility of individuals. The conclusions of RCEP are that the epidemiological literature is vastly complex and controversial. Some studies indicate a link between exposure to pesticides and chronic ill-health, but many others have failed to establish any significant link. CFS and MCS would not become apparent with the current animal tests required for pesticide approval. The overriding conclusion by RCEP is that a link between pesticide exposure and chronic ill-health is plausible and can, thus, not be excluded. They propose the development of suitable animal tests for CFS and MCS, and in the meantime a precautionary approach.
On the basis of these presumed uncertainties, the precautionary principle is used as the interim solution for the period that these uncertainties are not solved. The RCEP report proposes a buffer zone of 5 m between the spraying and the border of the residential property. Furthermore, the farmer should inform the residents in advance about the spraying.
Commenting on the health issues aspect of the report, COT/COC (2006) has come to the conclusion that there is no scientific basis for an additional precautionary approach to the risk assessment of pesticides, as proposed by RCEP. The two scientific committees agreed with another RCEP recommendation that a review of the literature on CFS and MCS should be undertaken. They did indicate that the current literature indicates that psychological issues might be involved and that odour (some pesticide formulations have a bad smell) and the involuntary nature of exposure are important factors. It is stated to be impossible to design animal tests when the cause of the health effect is not known.
Since the role of ACP has come under some criticism in the RCEP, it is no surprise that ACP in turn has critically evaluated the RCEP report (ACP, 2005). In its comments, ACP (2005) regards the 100-fold safety factor mentioned above as dealing adequately with bystander exposure. ACP states that over the years 2000–2005 it considered 38 active substances, of which only nine exceeded 10% of the AOEL for the bystander/resident. ACP indicates that these belong to special cases (e.g. use as soil fumigants, seed potato treatment, use in animal and poultry houses), but for four active substances this related to orchard spraying, and only one dealt with field application. This last one was, however, a special case and was treated extremely conservatively on other grounds. The only real exceptions were the four active substances, which were approved for orchard spraying, and the smallest margin of safety was estimated for one case where the exposure value used for the risk assessment was similar to the AOEL.
Experiences such as mine with the aerial spraying might be taken as supporting a precautionary approach, but ACP (2005) and BCPC (2006) challenge the RCEP's proposal, on the grounds that the assessment, although there are some uncertainties to be resolved, takes sufficient care of some extreme situations. Furthermore, no one would voluntarily stand next to a spray boom in action. A farmer should not spray in the direct vicinity of a residence, unless there is some border.
ACP (2005) stresses the disadvantage of over-precaution even beyond the loss of benefits. It would send a misleading message to the public and might even distract from other more pressing problems such as unsatisfactory storage of pesticides in people's homes. Precautionary actions in response to scientific uncertainty must be proportionate (ACP, 2005). ACP considers many of the recommendations of RECP as disproportionate.
The RCEP report (2005) has listed a large series of recommendations. Many of them relate to the alleged uncertainties and propose a way to solve them. BCPC (2005, 2006), COT/COC (2006) and ACP (2005) have challenged many of the recommendations. ACP has considered each of the recommendations separately with appreciable detail.
A personal response
I am impressed by the scientific and verbal care with which ACP has treated the RCEP report. The RCEP report indeed has several flaws in itself. It proposes a 5 m buffer zone without any argument why this should be 5. It proposes the development of new test systems but proposes no methodology or other clue to how this should or could be done. How do you design an animal test when you do not know the etiology of the alleged health effect in humans? RCEP proposes a probabilistic approach for estimating bystander and residential exposure, whereas they should know, and do not acknowledge, that such an approach requires a huge amount of data that will not be available in many years to come.
It is clear that the quality of the ACP reply, accepting a lack of transparency in the current risk assessments, acknowledging several uncertainties, and also accepting some recommendations of the RCEP report on targeted studies of biomarkers in residents and on a literature evaluation for CFS and MCS, is much higher than the quality of the RCEP report itself. It does appear that the expertise of the RCEP did not cover the issues at hand very well, and this is an incident that should not be allowed to happen again. The lack of expertise within the RCEP, though compensated by external experts for the present purpose, was acknowledged by its secretary (BCPC, 2005; p. 86).
I believe that it is clear that some residents have experienced ill-health which they perceive to be related to pesticide exposure. Whether a causal link to exposure can ultimately be demonstrated or not, the effects themselves cannot be dismissed. Although the introduction of a general buffer zone for all farms and residences may be an over-reaction to this, and not justified on scientific grounds, it seems also clear that farmers should be mindful of the possible reactions of people living on lands close to fields that have to be treated. It seems also likely that the approach usually taken in the risk assessment for pesticides, which has already thoroughly addressed the issue of bystanders and residents, can be further improved using more targeted data than currently available. A special case for consideration might be orchard spraying, where apparently the margin of additional safety between AOEL and estimated exposure was observed to be relatively small (see above for four cases). It seems absolutely clear that for soil fumigation, each product should be considered on a case-by-case basis. In that case, one is generally dealing with volatile fumigants that evolve or develop during and after the application for quite some time after application.
Risk management in whatever way, should take account of not only the costs of additional measures but also of the presumed benefits. This has to do with quality of life for individuals, but also with economic burdens for other individuals and society as a whole (locally and at large). Proving or establishing a zero risk is impossible, and should not be the focus of our regulations and thus our risk management approaches.
It is a pity that in other European countries there does not seem to be much attention for the issues that have got such a wide and thorough treatment in the UK.
I would like to congratulate the UK community for this thoroughness, although it is also clear that it will not satisfy the campaigners and will not help the alleged victims very much.
The British government response to RCEP
The British government's 28-page response to the RCEP report was published in July this year (DEFRA, 2006) just after submission of the initial version of this commentary. Reactions to the points discussed above include the following (paragraph numbers apply to the response).
- RCEP said that it could not rule out a link between resident and bystander exposure and chronic ill-health, felt that this indicated an urgent need for research, and recommended a more precautionary approach. The government does not support the recommendations either for urgent research or precaution beyond that already built into the process. (para 18)
- RCEP recommended a comprehensive systematic review of the literature on pesticide spraying and human health. The government supports COT/COC in favouring smaller more directed reviews, but will consider a feasibility study of a comprehensive review. (paras 21–22)
- RCEP recommended the use of novel investigative methods such as magnetic resonance spectroscopy and gene and protein profiling. The government feels that any investigation of CFS and MCS using these techniques should not be confined to the alleged link with bystander pesticide exposure. (paras 24–25)
- RCEP recommended development of new animal models to investigate the chronic disorders reported by bystanders. The government feels that there is ‘no rationale’ for this ‘without a clear mechanistic basis’. (para 30)
- RCEP recommended that the current approach to bystander exposure assessment should be replaced by a probabilistic computational model backed by wind tunnel and field tests, which should be field validated, peer reviewed, and published in the open literature. The government defended the present system, but basically agreed that some changes were needed. (paras 44–52)
- RCEP recommended a 5 m buffer zone. The government rejected a statutory buffer zone as a disproportionate response, but suggested that local ones might be worked out between farmers and residents! (paras 58–60)
The news release announcing publication of the response said that of RCEP's 35 recommendations, the government accepted, will consider, or is already doing 25 of them. However, of the issues discussed in this commentary, the response leaves an overall impression of backing CoT/CoC and ACP rather than RCEP. However, it seems likely that there will be a review of the exposure assessment model, and that a new model will be peer-reviewed and that the process will become more open.
It was further indicated by the government that the UK would take a primary role on the present issue in Europe, taking the lead in revising some of the current approaches, so this is clearly a matter that will continue to be of interest, both from the point of view of public interest, research and regulation.
Received June 29, 2006; in final form July 29, 2006
REFERENCES
A commentary on the report published by the Royal Commission on Environmental Pollution in September 2005 ACP, Advisory Committee on Pesticides. (2005) Crop spraying and the health of residents and bystanders. Available from http://www.rcep.org.uk/cropspraying.htm (Accessed on 29 July 2006).
Aeraqua. (2005) A study of presentations of householder concerns to the painted apple moth (PAM) health service, and Auckland Summer Symptom Survey. (Aeraqua Medical Services Ltd, Auckland, New Zealand) Available from http://www.biosecurity.govt.nz/files/pests-diseases/forests/painted-apple-moth/pam-health-report.pdf (Accessed on 28 July 2006).
BCPC. (2005) Review of the Report of the Royal Commission on Environmental Pollution on Crop Spraying and the Health of Residents and Bystanders. Proceedings of a special discussion meeting held on 1 November 2005 during the BCPC International Congress in Glasgow(BCPC Publications, Alton, Hampshire) ISBN 1 901396 41 X.
Commentary by BCPC (formerly The British Crop Production Council) (May 2006) BCPC. (2006) Royal Commission on Environmental Pollution Report in Crop Spraying and the Health of Residents and Bystanders. Available from http://www.bcpc.org/reports/docs/20060517.pdf. (Accessed on 28 July 2006).
COT/COC, Committee on Toxicity and Committee on Carcinogenicity of Chemicals in Food, Consumer Products and the Environment. (2006) Statement on Royal Commission on Environmental Pollution: Crop Spraying and the Health of Residents and Bystanders (April 2006). , UK: Department of Health Available from http://www.advisorybodies.doh.gov.uk/cotnonfood/rcep.htm (Accessed on 29 July 2006).
CSL, Central Science Laboratory. (2001) Pesticide Usage Survey Report 184. Aerial Applications Great Britain 2001. Available from http://www.csl.gov.uk/science/organ/pvm/puskm/aerial2001.pdf (Accessed on 29 July 2006).
Crop spraying and the health of residents and bystanders DEFRA. (2006) UK Government response to Royal Commission on Environmental Pollution's special report. Department for Environment, Food and Rural Affairs. Available from http://www.defra.gov.uk/environment/rcep/pdf/rcepcropspray-response.pdf (Accessed on 27 July 2006).
EUROPOEM, European Predictive Operator Exposure Model. (2002) The Development, Maintenance and Dissemination of Generic European Databases and Predictive Exposure Models to Plant Protection Products. Report to DG SANCO (FAIR3 CT96-1406), Brussels, Belgium.
RCEP, Royal Commission on Environmental Pollution. (2005) Crop Spraying and the Health of Residents and Bystanders, RCEP, London, UK. Available from http://www.rcep.org.uk/cropspraying.htm (Accessed on 29 July 2006).
In Van Hemmen JJ and van der Jagt KE (Eds.). Innovative exposure assessment of pesticide uses for appropriate risk assessment. Ann Occup Hyg (2001) 45:suppl. 1, s1–s174.
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