Post-application exposure

Lack of ensuring that there is no post-application exposure. Excretion curves for several workers in our studies indicate that occasionally some avenue of re-exposure occurs after the actual spray day. 

USEPA (1998a). Post Application Exposure Guidelines Series 875 - Group B, Environmental Protection Agency, Office of Prevention, Pesticides and Toxic Substances, Washington, DC, USA (website http //www.epa.gov/oscpmont/sap/1998/march/contents.htm). 

Given that the potential for post-application exposures largely exists due to product use in and around the home, the need to develop and validate models for prediction of multi-pathway, multi-route exposures and absorbed dose is... 

The application of pesticides is widespread in agriculture and elsewhere, and the concomitant risks depend on their toxicity, and duration and frequency, as well as the level of exposure (Henderson et al., 1993 Krieger and Ross, 1993). Exposure may be incidental or almost continuous. This is true not only for workers (occupational exposure), but also for the general public and people who may be considered as bystanders, who are not involved in the actual occupational activities with pesticides, but are close enough to get exposed. In this present chapter, only operator exposure will be discussed because agricultural re-entry modelling is discussed in Chapter 2 and residential post-application exposure modelling in Chapter 6 of this book. 

Of special interest is post-application exposure of toddlers and children, who tend to play on the floor and show extensive mouthing behavior (Davis and Ahmed, 1998 Groot et al., 1998). Toddlers and children contact residues which have settled on the floor by wiping the floor and stirring up dust. Semivolatile and volatile pesticides evaporate and absorb onto various surfaces, including babies toys, which have extensive contact with children (Gurunathan et al., 1998). In addition, the low body weight compared to adults is a risk factor for toddlers and children. 

USEPA (1997a). Post Application Exposure Monitoring Test Guidelines, Series 875 - Group B - Occupational and Residential Exposure Test Guidelines, Version 5.3,... 

An individual may have non-dietary exposure from multiple pesticide uses at different times of the year (Figure 8.19). A use may involve one or more chemicals, applicator exposure and post-application exposures on several days. The temporal occurrence of use events, the algorithms for calculating the time-dependent dose given that a use has occurred, and the individual s behavior generate chemical and route-specific dose profiles. These profiles are combined over the different uses to produce the chemical and route-specific dose profiles over time for the non-dietary sources. 

The USEPA has spearheaded a similar tiered approach for application and post-application in residential exposure scenarios. With the US Food Quality Protection Act (FQPA) as impetus, the USEPA has developed a series of algorithms which yield Tier 1 estimates for a broad range of residential application and post-application exposure scenarios. Approximately 40 unique scenarios are addressed in the USEPA s draft Standard Operating Procedure for Residential Exposure Assessment (USEPA, 1997c). Although some jurisdictions, including Canada, have adopted some of these algorithms. Tier 1 approaches for residential scenarios have not been the subject of substantial international discussion to date. 

Transferable and dislodgeable residue studies are an important tool for characterizing post-application exposure potential. Analysis of these data requires characterization of dissipation kinetics. This raises a number of data analysis questions, including the following ... 

The approach taken to these issues can significantly influence post-application exposure assessments and lead to divergent outcomes by regulatory authorities. Harmonized approaches to analysis of dissipation kinetics are therefore needed. 

Methodological guidance for deriving transfer metrics for post-application exposure scenarios in agricultural settings when the treated surface of interest is not foliage, e.g. soil. 

Bergeron, V., C. Norman and J. Worgan (1997). Workshop on Post-Application Exposure Assessment, Final Report, Toronto, ON, Canada. 

Secondary exposure (biocides) Post-application exposure via the enviromnent, namely bystanders and consumers, including children, who may be inadvertently exposed to wood preservatives by inhalation, dermal contact or by ingestion, and have little or no control over this exposure (OECD, 2000). 

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