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Accessible Unlicensed Requires Authentication Published by De Gruyter December 9, 2020

Current knowledge on urease and nitrification inhibitors technology and their safety

Aishwarya Ray, Chikere Nkwonta, Patrick Forrestal, Martin Danaher, Karl Richards, Tom O’Callaghan, Sean Hogan and Enda Cummins



Urea is one of the most widely used commercial fertilisers worldwide due to its high N density and cost effectiveness. However, it can be lost in the form of gaseous ammonia and other greenhouse gas (GHG) emissions which can potentially lead to environmental pollution. Farmers are compelled to apply more urea to account for those losses, thereby increasing their expenditure on fertilization. The objective of this paper is to present a literature review on current knowledge regarding inhibitor technologies such as urease inhibitor; n-(N-butyl) thiophosphoric triamide (NBPT), and nitrification inhibitor; dicyandiamide (DCD).


A thorough review of all the scientific literature was carried out and a proposed risk assessment framework developed.


The study showed that the urease inhibitor NBPT significantly reduced NH3 loss from urea. However, concerns about NBPT safety to human health had been raised when the nitrification inhibitor DCD appeared as a residue in milk. This article presents a risk assessment framework for evaluating human exposure to chemicals like NBPT or DCD, following the consumption of foods of animal origin (e.g. milk) from cows grazing on inhibitor-treated pasture.


The EU’s target of a 40% reduction of greenhouse gas emissions by 2030 can be aided by using NBPT as part of an overall suite of solutions. A comprehensive risk assessment is advised for effective evaluation of potential risks from exposure to these inhibitors.

Corresponding author: Aishwarya Ray, School of Biosystems and Food Engineering, University College Dublin, Belfield, Dublin 4, Dublin, Ireland, E-mail:

Funding source: Department of Agriculture, Food and the Marine

Award Identifier / Grant number: 17/F/207

  1. Research funding: This work was supported by the Department of Agriculture, Food and Marine (DAFM), Ireland [Grant Number: 17/F/207].

  2. Author contributions: All authors have accepted responsibility for the entire content of this manuscript and approved its submission.

  3. Competing interests: Authors state no conflict of interest

  4. Informed consent: Not applicable.

  5. Ethical approval: Not applicable.


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Received: 2020-07-21
Accepted: 2020-11-04
Published Online: 2020-12-09
Published in Print: 2021-12-20

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