PhD: Determination of the key parameters influencing dislodgeable foliar pesticide residues

2019 - 2022

This PhD seeks to better understand the factors that affect the amount of pesticide residue on plant foliage that, on contact, can be transferred to human skin and clothing (Dislodgeable Foliar Residues - DFRs). This type of information can help evaluate:

  • Occupational exposure: Of farmers in their working environment. For example, by establishing the period of elapsed time needed following greenhouse spraying before it is safe to re-enter.
  • Bystander exposure: Ensuring that members of the public entering treated crop areas, do not encounter unacceptable risks.

Previous research has shown that there is a relationship between the proportion of residue that is dislodgeable and a range of factors including the pesticide application rate, chemical characteristics, product formulation, environmental conditions (including temperature and humidity), and the plant architecture and leaf type. These issues are not fully understood, therefore the purpose of this 4-year work programme is to explore some of these issues with the intention of enabling the refinement of re-entry risk assessments.

The poject is being run jointly by the University of Hertfordshire and Syngenta’s prestigious international research centre at Jealott's Hill, Berkshire.


Prof Kathy Lewis

Appointed student

Mohamed Badawy


  • Badawy, M.H., Morgan, N. & Lewis, K.A. (2021). Correlation between dietary and dislodgeable foliar (DFR) crop residues decline data: a proposed approach to refine non-dietary risk assessment. Regulatory Toxicology and Pharmacology, Preprint. DOI.
  • Poster

University of Hertfordshire
University of Hertfordshire, 2017.