Charles Henry Roussel’s interview
Trained as an agronomist, Charles-Henry started his career as a field trialist. He has been acting as Study Director in residue studies since 1998 and developed Human Exposure studies since 2009. Charles-Henry joined Staphyt’s GLP team in 2005 and is now in charge of study management, i.e. developing the study plan, monitoring the different phases and reporting the study results in a final report. He ensures a close link and optimal communication between the various study stakeholders and the sponsor, in compliance with GLP requirements for multi-site studies (OECD No. 13).
What are human exposure studies?
Human exposure studies are developed to quantify information on potential non-dietary systemic exposure as part of the regulatory risk assessment for PPPs.
In accordance with Regulation (EC) No 1107/2009, risk assessments must be carried out for all scenarios of exposure of operators, workers, residents and bystanders that can be expected to occur as a consequence of the proposed uses of a plant protection product (PPP) according to Good Agricultural Practices (GAP). To assist risk assessors and applicants when quantifying potential non-dietary exposure, the EFSA Guidance on the assessment of exposure of operators, workers, residents and bystanders in risk assessment for plant protection products was issued in 2014 and revised in 2021 (EFSA, 2022).
Why and when such studies are required?
Human Risk Assessment is required in the frame of the Regulations (EC) No.1107/2009 and (EU) No.284/2013 during the authorization process of plant protection products to evaluate the exposure of operators, workers (re-entry), residents and bystanders during their uses.
As a first step, appropriate exposure models (such as AOEM – Agricultural Operator Exposition Model) are required to estimate these exposures through calculated daily intakes to be compared with a maximum exposure dose level (AOEL for Acceptable Operator Exposure Level). Using some default values, the exposure to the plant protection product calculated by the model can be unacceptable (above the AOEL) for one or more of the defined categories of person (operator, worker…). Consequently it needs to be refined by generating new exposure data (such as dermal absorption study, Dislodgeable Foliar Residue DFR Trials…).
OPEX studies are required as a final step when models can’t provide any acceptable refined exposure risk assessment for operators, workers (re-entry), residents and/or bystanders. The purpose of the OPEX studies is to generate quantified data in real conditions of use and to elaborate the risk assessment of human exposure in a treatment area. They encompass people working in the field (operator/worker) or around the field (bystander/resident). Various routes of exposure (inhalation and dermal in different areas) are studied. The general requirements are based on OECD No. 9 with reference to the US guidelines of EPA OPPTS 875.1300 and OPPTS 875.2500.
How do we conduct such studies?
1. Field phase
The first step is to set up the study design. The following parameters are defined: number of locations, number of operators, type of application technique, (PPE) personal protective equipment worn, type of dosimeters (dermal, inhalation or biomonitoring) …
- Selection and preparation of the site are done according to the study plan. The extensive Staphyt experimentation network allows sites to be selected with willing and collaborative growers in representative growing areas. Staphyt carries out multi-site studies on all cropping systems, in all regulatory zones in the North and South of Europe and beyond.
- Exposure (application, re-entry, fumigation) done according to GAP
- Monitoring of the operators during the exposition period
- Specimens are collected, cut, identified and frozen before transport to the lab.
- Field QC (quality control) are made for each matrix and exposed to the test item and subjected to the same conditions of the trial. These values will allow the correction of the results observed for any losses recorded during the process of exposure, sampling, freezing, shipping and the analytical process at the Test Site laboratory.
2. Analytical phase
Our refrigerated (<-18°C) transport network delivers samples to our partner laboratories throughout Europe. More than 250 residue analyses including multiple matrices may be required for a single study.
Why choose Staphyt for your OPEX studies?
- The experience of the teams: studies carried out every year for more than 20 years
- Agronomic expertise in various crops (field, horticulture, orchard, grapevine, ..) and systems (greenhouse, open-field, post harvest)
- Large network of partner growers
- An in-house study management team
- The support of the Staphyt Regulatory Affairs team in the support, modeling, calculation of concentrations in the environment and risk assessments required by the authorities
Article contributors:
Charles Henry Roussel, Study Director
Romain Galy, Toxicologist
Célia Bastiani, Business Development Residue
