Fenuron

Endpoint summary

Description of key information

A basic toxicokinetics literature search and assessment was performed for the toxicokinetics profile of Fenuron (given below in additional information and as attachment to this record). This includes absorption and distribution, metabolism, excretion and enzyme induction properties. Fenuron is assessed to be well absorbed via both the gastrointestinal and respiratory tract (considered at 100% absorption from conservative viewpoint), whereas dermal absorption is lower (considered at 50% absorption from conservative viewpoint). Fenuron (like urea herbicides) is considered to be metabolised to mono-or di-dealkylated metabolites, which are water soluble and excreted in the urine, therefore bioaccumulation is not likely.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Absorption rate - oral (%):

100

Absorption rate - dermal (%):

50

Absorption rate - inhalation (%):

100

Additional information

Absorption of Fenuron was assessed as follows based on physicochemical/toxicological data:

- Fenuron is a white odourless solid with mean particle diameter of2.32 µm (respirable). It has a molecular weight of164.2044 g/mol, logP of 0.98, low vapour pressure (0.0021 Pa at 60°C)and is known to be soluble in water (3850 mg/L).

- Based upon the hydrophilic properties, particle size, water solubility and partition coefficient of Fenuron, oral absorption is considered to be likely. This is supported by the oral toxicity findings observed with Fenuron. From a conservative viewpoint, a 100% oral absorption is considered.  

- Based on the particle size and partition coefficient of Fenuron, deposition in the deeper airways and absorption by inhalation is possible. As the molecule is water soluble, vapours may already be retained within the mucus of the upper airways. The oral toxicity data indicate that systemic effects are possible, however acute inhalation toxicity testing only showed local but not systemic effects. From a conservative viewpoint, a 100% inhalation absorption is considered.  

- Based on low molecular weight of Fenuron with rather high water and low vapour pressure, dermal absorption is possible but limited. When Dermwin is applied, dermal penetration rate seems to be rather low (Kp = 0.000841 cm/hr). From a conservative viewpoint, a 50% dermal absorption is considered. 

For the assessment of distribution, metabolism and excretion physicochemical and toxicological properties are taken into account.

- Based upon the low molecular weight and solubility in water, Fenuron is expected to be distributed in the body. This is supported by observed target organs and toxicity (haematological & clinical chemistry findings, increased liver weight).

- From information in literature, urea herbicides are metabolized as follows: mono-or di-dealkylated metabolites are produced by oxidation of alkyl chain of the terminal nitrogen atom.

- Excretion via the urine is expected because Fenuron is soluble in water and metabolites are likely to be present in urine.

- Based on basic toxicokinetics assessment, there are no predilection organs for accumulation, therefore no bioaccumulation is expected.