University Studies

WARF INSTITUTE INC, Madison, Wisconsin

Study showing the contamination hazard of the automatic pyrethrin dispensers in still air environment

UNIVERSITY OF ILLINOIS COLLEGE OF AGRICULTURE

Intermittent Pyrethrin Dispensers (IPD) and the probability of contamination

The studies completed at the University of Illinois on behalf of C.A.P. have shown that virtually no food residue hazard exists with the proper use of the IPD units.
A mathematical explanation of the emission rates and a degradation study of the materials is meaningful.
One IPD unit operating under recommended guidelines (100mg into 6,000 cubic feet) will result in a mathematically potential residue of 0.0066 ppm Pyrethrins, 0.0133 ppm Piperonyl Butoxide and 0.0223 ppm MGK 264 after one hour of operation on a small 300 gram TV dinner. This residue assumes complete fallout and 100 percent deposit on a square foot basis, which of course is unrealistic. Our tests have shown that only 1% of the aerosol emission is recoverable from a surface. When the residue tested above is applied to the TV dinner the resultant residue would be beyond the limits of detection.

The degradation rate of pyrethrin and the three synergists vary.

Half life studies indicate that MGK 264 is the first to go with piperonyl butoxide the last. It is interesting to note that when tropital is present the formulation tends to degrade at a greater rate than with other synergists, probably due to volatilisation. The following time loss study was used to determine the relative rates of degradation. The table cannot be applied to the same materials when emitted from IPD units as the particle size would increase the degradation rates significantly. Due to the ephemeral nature of the materials the table below reflects the appropriate half life values. The deposition of the materials was made at a rate of 1500 micrograms per square foot. This was accomplished by depositing a measured quantity of each material on individual sheets of filter paper 9cm in diameter.

Half life MGK 264 4hr
Half life Tropital 8hr
Half life Piperonyl Butoxide 72hr
Half life Pyrethrin 7hr

From this data was calculated that the loss rate per hour for the material on a square foot basis is:

MGK 264 188.0 ug
Tropital 94.0 ug
Piperonyl Butoxide 7.80 ug
Pyrethrin 107.0 ug

If one compares the rate of gain or accumulation from one IPD operating in a 6,000 cubic foot area and assuming that 100% of the material would fall out and deposit on a square foot basis. The following would result in one hour:

MGK 264 19.2 us/sq. ft
Tropital 11.6 ug/sq. ft
Piperonyl Butoxide 11.7 ug/sq. ft
Pyrethrin 5.8 ug/sq. ft

Tests have shown however that the actual rate of accumulation is about 1% of the above. These calculations further point out the improbability of accumulative residue as indeed the tests at the University of Illinois have shown.

Highly exaggerated use condition tests gave data showing insignificant levels of pyrethrin and the synergists were present in food after 21 days of continuous exposure. Other tests reflected no residue in milk or meat after 24 hours of exaggerated exposure.

With the data accumulated on the fallout hazard inherent with the IPD in food areas plus the instability of compounds it is a simple matter of arithmetic to determine that if pesticide residues were present, these residues would be far below the technical limits of the analytical method. In a recent test using tropital in place of piperonyl butoxide in still air after 12 hours of exposure the possible residues were less than 1 part per billion in meats, foods, sugar and coffee. Indeed the background interference of substances in the food made it impossible to detect pyrethrin, tropital or MGK 264.

In summary degradation rates far exceed accumulation rates when applied to the emission level of the IPD. This accounts for the lack of measurable residues in foods even when exposed under maximum conditions.

BIOLOGICAL TESTING LABORATORY, MINNEAPOLIS, MINNESOTA

-Intermittent Aerosol Efficacy – House flies in a 5,400 cubic foot chamber

Sample:

Konk Odourless
1.07% d-trans Allethrin
2.14% Piperonyl Butoxide
2.14% MGK 264
94.65% Inert Ingredients

Method:

Approximately 600 house flies (Musca domestica, F58t-II strain) were released into the 5,400 cubic foot chamber. The intermittent device was centred on a wall, 7 feet from the floor. The test aerosol unit, equipped with a metered valve, was placed in the device. The device was turned on, activating the aerosol valve every 15 minutes. Knockdown counts were taken hourly, for the first five hours, with a handheld counter. The test continued for 24 hours. The aerosol was weighed before spraying and again after spraying to determine dosage. A large dish containing sugarwater soaked pads was provided throughout the test period. The test was run in triplicate.

Modifications:

Device sprayed every 8 _ minutes. Knockdown counts were taken for the first four hours. Untreated controls run by releasing house flies into the chamber and taking knockdown counts as in actual test.

Summarised Results: