The substitution doctrine Special considerations given to children’s health

Public Health Significance of Urban Pests 485

14.2.2.4. Basing risk and exposure assessments on use patterns

Pesticide data sets and requirements, including risk and exposure assessments, are based on the pattern of use, and the safety database of the technical grade AI manufacturer is large. Most regulatory agencies also refer to these data as generic or core safety data. Application formatting requirements for pesticides are detailed, but are not harmonized between different regulatory agencies, although efforts continue to harmonize them. Also, testing protocols must be approved and testing conducted in facilities that comply with Good Laboratory Practices – a system of management controls for laboratories and research organizations to ensure the consistency and reliability of results.

14.3. Toxicology

4 This section covers two major areas: pesticide hazard identification and six groups of pes- ticides. In the WHO urban pests and health project, the primary focus is on exposure of residential bystanders and residential areas, not on professional pesticide applicators or food handling establishments. Hazards related only to the pesticides used most frequently for urban-pest management and pet treatments are considered.

14.3.1. Pesticide hazard identification

Pesticides are unique among chemical products, since a lot of toxicological information is available before marketing. Available data are mainly from tests on animals and this poses some problems in extrapolating and applying these data to people. These tests may not always be the most sensitive indicators of human response, but test data on people are limited, given that pesticides are toxicants. Bridging toxicology test results from one species to another is not foolproof. However, procedures have been devised to take this into account when assessing the risk to people of pesticide exposures. This section deals mostly with existing general toxicological information on pesticide poisoning and known toxic effects. Emphasis is on data that relate to people; when such data are absent or mini- mal, a summary of animal toxicological data is provided.

14.3.1.1. Acute toxicity

WHO classifies pesticides according to the acute risk to health – that is, the risk of sin- gle or multiple exposures over a relatively short period of time – that might be encoun- tered accidentally by any person handling the product, in accordance with the manufac- turer’s directions for handling or in accordance with the rules laid down for storage and transportation by competent international bodies. The classification distinguishes bet- ween the more and the less hazardous forms of each pesticide, in that it is based on the toxicity of the technical compound and on its formulations. In particular, allowance is made for the lesser hazards presented by solids, compared with liquids. The classification Pesticides: risks and hazards 484

14.2.2.1. The precautionary principle

The precautionary principle is the all-embracing principle and so-called force behind the regulation of chemicals. T he principle is the foundation of regulating chemicals in Europe, and although federal level regulatory authorities in the United States and Canada have never adopted this principle as a formal creed per se, it is gaining popula- rity with some local authorities in the United States. Expressed in another way, when scientific certainty is lacking, precaution should be applied to the breadth of regulatory concerns. All regulatory agencies and authorities that register pesticides conduct thorough and extensive health and environmental reviews of pesticides before allowing their initial or continued use in the environment. Perhaps the best understood reason for applying pre- caution to pesticide regulation originates in the general abstinence from conducting or permitting tests with pesticides on human subjects. Therefore, toxicology data are brid- ged from animal testing to assess the risk of adverse effects on people. Also, computer models are used to refine exposure and risk assessment. Moreover, the special considera- tion now given to children’s health in the pesticide risk assessment process enhances pre- cautionary measures and is at the forefront of regulatory considerations.

14.2.2.2. The substitution doctrine

Simply defined, the substitution doctrine advocates, and in some regulatory scenarios requires, the substitution of a less hazardous pesticide for a more hazardous pesticide when an alternative is available. Supporters of this doctrine see its application to pesticide regulation as an opportunity to encourage research and development of less hazardous pesticides. Critics believe that application of this doctrine will lead to production, regis- tration and use of less efficacious pesticides, especially when pest control is needed for public health and that this condition conflicts with free market forces, thus failing to meet consumer demands. Critics have also implied that such a condition places the public at risk.

14.2.2.3. Special considerations given to children’s health

All major pesticide regulatory agencies in Europe and North America give special consi- deration to protecting children’s health. Aside from the high political and social value given to protecting future generations, epidemiological evidence shows a relationship between certain children’s ailments and chemicals. Disorders that result from exposure to heavy metals are well-known examples. Also, children have more life ahead of them than do adults, and this may be important for those health risks that result from the accu- mulation of doses or effects over a long period of time. Risk assessors in the United States, as required by law, presume that children are more susceptible to adverse effects from pesticides. Therefore, an additional margin of safety usually tenfold is applied to pro- tect infants and children from risks posed by pesticide residues in food and to protect them when pesticides are used in and around homes and schools. In the EU, a special directive known as the Baby Food Directive has set at 0.001mgkg taken as an enfor- ceable zero level in practice the maximum level of any pesticide residue admitted on food destined for infants. A global guide to resources on chemical safety and children’s health has been published by IFCS 2005. 4 Data on acceptable daily intake and acute reference dose reported below have been established by the FAOWHO Joint Meeting on Pesticide Residues JMPR and can be found in the Inventory of IPCS and other WHO pesticide evaluations and summary of toxico- logical evaluations performed by the Joint Meeting on Pesticide Residues JMPR WHO IPCS, 2006b. Public Health Significance of Urban Pests 487 an acute hazard in normal use no category. Most of the recently registered compounds are classified as presenting slight or no acute hazard. For our discussion on pesticide hazards in residential settings, Fig. 14.2 shows the oral LD 50 values for rats for some of the most commonly used household biocides. 14.3.1.1.1. Epidemiology of acute pesticide poisoning Our knowledge of the effects of pesticides on people generally comes from reports of acute poisoning that occur worldwide. Acute pesticide poisoning can result from inten- tional, occupational or accidental exposure to pesticides, but worldwide figures of pesti- cide poisonings are not available. WHO the United Nations Environment Programme WHO, 1990 estimated an annual incidence of unintentional acute poisoning of about 1 million people, with an overall mortality rate of about 1 of which only 1 is in middle- and high-income countries. The majority of unintentional pesticide poisonings are occu- pational, although cases occur in the general population due to improper use or storage of pesticides intended for amateur uses or in-house pest control. The most hazardous compounds cause the majority of these poisonings. Population-based studies in 17 coun- tries gave annual incidence rates of unintentional pesticide poisoning of 0.3–18.0 cases per 100 000 population Jeyaratnam, 1990. Pesticides are estimated to be responsible for less than 4 of deaths from all types of acci- dental poisoning, based on reports from poison control centres: the apparent increase in the number of cases in recent years may reflect increased use, but it may also reflect the availability of better statistics. The estimated annual incidence of intentional acute poi- soning is about 2 million people, with a 5.7 mortality rate, which appears to be higher in low-income countries up to 23 WHO, 1990. Suicide attempts usually, but not exclusively, with organophosphorous compounds represent 44–91 and 26–60 of acute pesticide poisonings in South-East Asia and in Central America, respectively, whereas in California all non-occupational pesticide poisonings represent about 5 of the total Jeyaratnam, 1990. An unknown fraction of these attempts involves pesticides intended for uses other than agriculture. WHO Peden, McGee Krug, 2002 reports accidental pesticide poisonings as the ninth leading cause of death.

14.3.1.2. Toxicity end-points