Fenarimol was reviewed for the first time by the 1995 JMPR and a number of maximum residue levels were estimated. Although data on the environmental fate of fenarimol in soil were submitted to the Environmental Core Assessment Group at that Meeting they were not, as would normally be expected, submitted for the consideration of the FAO Panel. The manufacturer agreed to submit the data to the FAO for consideration by the FAO Panel at the 1996 JMPR. The 1995 Meeting decided that in these circumstances the maximum residue levels should be recommended only as temporary MRLs with a requirement for the environmental fate studies. The manufacturer has now submitted data on the environmental fate of fenarimol in soil.
The 1995 Meeting concluded that a maximum residue level of 5 mg/kg for dry hops would be appropriate but, since samples in the relevant trials were stored for 13 months before analysis, decided not to recommend an MRL for hops in the absence of data confirming the stability of fenarimol in a leafy crop. A study of the stability of fenarimol residues in dried hops has now been submitted.
The rate of aerobic degradation in the laboratory was examined in five soils in the dark in two studies. These showed that at 20-24°C the degradation of fenarimol was very slow with a half-life of 436-1833 days. The production of CO2 was low (<5%) over the 180- and 365-day studies, as were the levels of unextractable residues which amounted to 3.3-17.2% of the applied radioactivity (AR). The levels of degradation products were also low (up to 4.1%) and only one of the compounds was identified, a-(2-chlorophenyl)-a-(4-chlorophenyl)-1,2-dihydro-2-oxo-5-pyrimidinemethanol.
Dissipation under field conditions was investigated in two recent studies at six sites across Germany. Although samples were taken from several depths at some of the sites, only 0-20 cm cores were analysed in all the trials. At two sites (Grebin and Alsfeld) very high concentrations of fenarimol at day 0 (three to four times those predicted from the application rate) resulted in short DT50 values. Over all the trials the DT50 values ranged from 14 to 130 days (60-130 days excluding the Grebin and Alsfeld sites). Fenarimol persists in the soil and in five of the studies the DT90 value was more than one year. An earlier study in the USA gave a half-life of 112 days for fenarimol applied to the surface. When fenarimol was incorporated into the soil the half-life was >903 days with 35% of the AR as fenarimol, 13% unextractable and 9% extractable but unidentified after 511 days.
In further studies at four US sites fenarimol was lost slowly from bare soil with average DT50 values ranging from 98 to 651 days. The rate of dissipation appeared to increase with increasing soil moisture.
Four soils were examined to determine sorption, and Koc values in the range 500-992 g/ml were calculated. In column leaching experiments with four soils the overall recovery of radioactivity was not high, but only 0-0.4% of the recovered radioactivity was found in the leachate after about 1.7 litres had been collected. Most of the of the radioactivity (91-100%) was recovered from the top 10 cm of the soil column. When fenarimol was incubated in soil for 30 days before leaching 0.28-0.32% of the AR was found in the leachates from columns of four different soil types. Slightly more radioactivity (1.7-9% of the AR) was leached when fenarimol-soil mixtures were aged in sunlight and the degraded fenarimol applied to a soil column. The majority of this radioactivity was found to be from o-chlorobenzoic acid.
In a photolysis experiment in Indiana, USA (maximum temperature 18°C), in which fenarimol was deposited in baking dishes and exposed to natural sunlight, 33-38% of the initial fenarimol was still present after 100 days. In a further study of irradiated mixtures in which 40-50% of the [14C]fenarimol had been degraded, more than 50 low-level photodegradation products were separated but no major products were detected. In contrast a further experiment in Indiana showed no photolysis of fenarimol on a soil surface after 32 h exposure.
In a study of aqueous photolysis the major tentatively identified photodegradation product was 2'-chloro-2-(5-pyrimidinyl)-4-chlorobenzophenone, which accounted for 17% of the AR after 4 h incubation. Ten other unidentified products were observed, each accounting for <3.3% of the AR.
The Meeting considered these data on environmental fate to be satisfactory and recommended the use of the maximum residue levels estimated by the 1995 Meeting as MRLs, which should no longer be temporary.
Data on the stability of fenarimol in stored analytical samples of dry hops were reviewed. Residues were stable up to 2 years in dry hops fortified at 1 mg/kg and stored at <-16°C. The Meeting decided to recommend the maximum residue level of 5 mg/kg provisionally estimated by the 1995 JMPR for use as an MRL.
The Meeting noted the high persistence of fenarimol in soil, and recalled that the 1995 Meeting had listed as desirable a study to assess the likely residues in relevant succeeding or rotational crops. The 1995 JMPR report (Section 2.5.2) referred to the need to submit data on the uptake of compounds by crops from the soil.
The Meeting was informed that no data were available on the uptake from soil by crops, the bioavailability of fenarimol, or residues in rotational/succeeding crops, but a rotational crop study would be completed by 1997 and the data from it would be made available to a future Meeting.
