Brian D. Ripley

Investigations of pesticide contaminations in rural wells, 1979–1984, Ontario, Canada

Between the years 1979 and 1984, investigations were conducted into 311 events of suspected contaminations of wells with pesticides. This involved the analyses of water from 359 wells where the suspected contamination originated from (i) spills (ii) spray drift or (iii) surface runoff waters carrying pesticides into wells. Investigations covered 83 spill events involving 104 rural wells; tests revealed 79 of these became contaminated. The contaminations were caused by (i) spills of pesticide concentrates (ii) back-siphoning of spray solutions and/or (iii) spills from overfilling, emptying or rinsing spray equipment. The pesticides either entered directly into the wells or contaminated the area in the vicinity of the wells. In spite of cleanup attempts, difficulty was experienced in decontaminating most well waters and some had to be abandoned. The longest period of monitoring a contaminated well was 1, 117 days; during that time the decline in residue was slow.Investigations were made into 228 events involving 255 wells where spray drift and/or surface runoff waters with pesticides were observed as entering the well; however, only 55 were found to contain detectable residues. The highest proportion of these events was associated with surface runoff or spray drift from cornfields; of 86 wells involved only 26 contained measurable residues and all involved atrazine. Fifty-seven well investigations were associated with spraying right-of-ways and 16 waters were contaminated with 2,4-D and dichlorprop. The remaining 13 well contaminations were associated with various other land-use activities. It required 45 to 347 days to decontaminate these 55 wells.

Survey of farm wells for pesticides residues, Southern Ontario, Canada, 1981-1982, 1984

Water samples from 11 wells located in an area of intensive vegetable production on an organic soil were collected in 1981 and 1982, and analyzed for pesticide residues. Residues of diazinon, malathion, allidochlor, linuron, and prometryne were identified in four of the wells.Water samples from 91 wells were collected from farms on mineral soils across Southern Ontario during 1984 and analyzed for pesticide residues. Atrazine residues (0.1 to 74 μg/L) were present in 11 wells and trifluralin residues (41μg/L) contaminated one well. The highest residue of atrazine (74 μg/L) was present in one well along with contamination of three other herbicides and one insecticide. This was the result of a spill into the drilled well that gave residues of each component between 22 and 125μg/L. After 10 months of cleaning, this well was still contaminated.

Residues of insecticides, and fungicides in fruit produced in Ontario, Canada, 1986-1988.

Between 1986 and 1988, 306 composite samples of fruit representing eight commodities were collected from farm deliveries to the marketplace in Ontario, Canada. All samples were analysed for insecticides and fungicides. The analysis procedure included tests for organochlorine, organophosphorus, synthetic pyrethroid and methylcarbamate insecticides and dithiocarbamate, dicarboximide and organochlorine fungicides. The commodities tested included apples, blueberries, cherries, grapes, peaches, pears, raspberries and strawberries. In 14% of all fruit samples, pesticide residues were below the detection limits, which ranged between 0.005 and 0.02 mg/kg. A further 14% had total combined pesticide residues below 0.1 mg/kg. Total combined fungicide and insecticide residues ranged from 0.1 to 11 mg/kg in 72% of samples. Six different pesticides were in violation of maximum residue limits (MRL) on 11 (3.6%) of fruit samples. Captan exceeded the 5 mg/kg MRL in five samples and EBDC exceeded the 7 mg/kg MRL in two. Other violations included single fruit samples with dicofol, endosulphan, phosalone and iprodione above the MRL. Raw grapes harvested for wine contained residues of 10 pesticides and the number changed little following the crushing of the grapes; however, fermentation into wine significantly reduced residues. Six insecticides and four fungicides were present on the raw grapes and 4/105 were above the MRL. Following crushing, four insecticides and five fungicides were identified and 4/40 were above the MRL. In wine only three insecticides were identified and all were well below the MRL. Carbaryl appeared to be the most persistent, declining very little between raw grapes and wine.

Residues of ethylenebisdithiocarbamates on field-treated fruits and vegetables

The ethylenebisdithiocarbamates (EBDC) are an agriculturally important and widely used group of broad spectrum fungicides. Currently these fungieides are recomanended by the Ontario Ministry of Agriculture & Food (O.M.A.F.) for use on many fruits and vegetables (O.M.A.F. PUBLICATION 360; 363; 367). A recent report in the FEDERAL REGISTER (1977), on the EPA rebuttable presumption against registration of the EBDC, documents the health hazard associated with these compounds because of their degradation to ethylene thiourea (ETU). There is considerable concern in the agricultural industry that several crops would have no recommended alternative fungicides if the EBDCs were restricted. There was an obvious need to confirm current O.M.A.F. recommendations on rate of application and days to harvest, to ensure that residues conformed with current Canadian pesticide residue tolerances on food products, and to compare Ontario residue data with those reported by other investigators. Previous studies in Ontario have been carried out on EBDC and ETU residues on pears (RIPLEY and SIMPSON 1977), on grapes (RIPLEY et al. 1978) and on tomatoes (RIPLEY and COX 1978). This paper presents data on EBDC residues determined on several fruits and vegetables following application of maneb (manganese ethylenebisdithiocarbamate) or zineb (zinc ethylenebisdithiocarbamate).

Monitoring Ontario‐grown apples for pest control chemicals used in their production, 1978–86

Between 1978 and 1986, 305 samples of apples were monitored for the residues of a wide range of pesticides used in their production. Three (1%) contained residues above the maximum residue limits (MRL) permitted under the Canadian Food and Drug Act and regulations; two involved phosalone at 5.9 and 6.2 mg/kg respectively and one involved diphenylamine at 6.7 mg/kg when the MRL was 5.0 mg/kg for both compounds. Low residues of dicofol, endosulfan, phosalone, phosmet, captan, daminozide and diphenylamine were frequently found; however they were well below the MRLs. These residue levels were correlated with survey data on the areas of the apple crop treated with specific pesticides. Residues of carbaryl, diazinon, ethion, azinophosmethyl, parathion, and dithiocarbamate fungicides were found occasionally; all were well below the MRLs and correlated with the pattern of use. No residues of PCB were found to a limit of detection of 0.01 mg/kg.

Residues of insecticides, fungicides and herbicides in fruit produced in Ontario, Canada, 1980-1984

Resultats de dosages systematiques realises sur des peches, cerises et fraises, en relation avec la reglementation sur les taux de residus de pesticides

Efficiency of water rinsing for the decontamination of used pesticide containers

The efficiency of water rinsings for the decontamination of emptied pesticide containers was investigated in the period 1979–1981; nineteen formulations representing seven insecticides and two fungicides were studied. Following normal emptying procedures, the amount of retained pesticides ranged from a low of 0.06% to a high of 7.48%. By successively rinsing with volumes of water equal to one-tenth of the volume of the containers, as many as five rinses were required to remove 99% of the retained formulation. When containers were held in an inverted position and allowed to drain one minute prior to rinsing, three successive rinsings were sufficient for most formulations to remove 99% of the retained pesticide. Decontamination by rinsing was achieved most readily with water-soluble concentrates and wettable powders while flowable suspensions appeared to be the most difficult to remove.

Residues of insecticides and fungicides on Ontario‐grown vegetables, 1986–1988

Between 1986 and 1988, 433 composite vegetable samples representing 16 commodities were collected from farm deliveries to the marketplace in Ontario, Canada. All samples were analysed for insecticides and fungicides. The analyses included organochlorine, organophosphorus, synthetic pyrethroid, and N-methylcarbamate insecticides and dithiocarbamate, dicarboximide, and organochlorine fungicides. The commodities tested included asparagus, beans, carrots, celery, cole crops, cucumbers, lettuce, onions, peppers, potatoes, radishes, rutabagas and tomatoes. In 64% of samples, no pesticide residues were identified to the limits of detection which ranged from 0.005 to 0.05 mg/kg. A further 22% had combined insecticide and fungicide residues below 0.1 mg/kg. Most of the positive findings were a fraction of the Maximum Residue Limit permitted for each commodity under the Canadian Food and Drugs Act and Regulation. Three samples (0.7%) had residues that exceeded the MRL. These involved diazinon and parathion on celery and chlorothalonil on peppers. While some commodities had no detectable residues others had measurable residues of up to three separate pesticides. The most were found on celery, lettuce and field tomatoes.