Ontario Farm Research Articles

In utero pesticide exposure and childhood morbidity

In humans, immune development begins early in embryonic life and continues throughout the early postnatal period. Although a number of pesticides have been observed to induce developmental immunotoxicity in mice, few human studies have examined the long term effects of in utero pesticide exposure on childhood morbidity. Empirical evidence suggests that the vulnerable period for toxic insults to the developing immune system extends from early gestation to adolescence in humans and animals. Using data from the Ontario Farm Family Health Study, we examined the relationship between farm couple exposures to pesticides during pregnancy and subsequent health outcomes in their offspring, including: persistent cough or bronchitis, asthma, and allergies or hayfever. No strong associations between pesticide exposures during pregnancy and persistent cough or bronchitis, or asthma were found. There was suggestive evidence that allergies and hayfever appeared to be more common in offspring, especially male offspring, exposed to certain specific pesticides during the period of pregnancy. Nevertheless, given the indirect indicators of pesticide exposure used in this study, and the scarcity of human studies on in utero exposure to pesticides and the development of allergies and other child health outcomes, these findings serve primarlily to generate hypotheses for future research.

Macrocyclic lactone-resistant Parascaris equorum on stud farms in Canada and effectiveness of fenbendazole and pyrantel pamoate

The aims of studies in 2002 and 2003 on three farms with 76 foals naturally infected with Parascaris equorum were to (i) identify if the nematode was resistant to ivermectin and moxidectin, and (ii) confirm the effectiveness of fenbendazole and pyrantel pamoate for the parasite. Twelve clinical trials, each with a Fecal Egg Count Reduction Test, were conducted on two Thoroughbred and one Standardbred farms in southwestern Ontario, Canada. In each trial, Parascaris eggs/g feces were estimated for each foal pre- and post-treatment using the Cornell-Wisconsin double flotation and Cornell-McMaster dilution techniques. On each farm and for each trial, foals were randomized into treatment groups. Treatments were ivermectin, moxidectin, fenbendazole, pyrantel pamoate administered at the manufacturers’ recommended dosages, and some foals were untreated. The overall efficacy for ivermectin was 33.5% (19 foals) and for moxidectin 47.2% (28 foals). Fenbendazole (16 foals) and pyrantel pamoate (21 foals) were highly effective for P. equorum each at 97.6%. For fenbendazole, 15 foals had 100% and for pyrantel pamoate 17 foals had >97% with 14 at 100%.

Sow shoulder lesions: Risk factors and treatment effects on an Ontario farm1

The objectives of this study were to identify risk factors for the development of shoulder lesions in lactating sows and to determine if an effective, economical, and practical treatment could be designed. The study was conducted at a 300-sow farrow-to-finish swine farm in Ontario between July and December 2004. Sow data were recorded on either the day of or 1 d after entering the farrowing crate and before farrowing had occurred. The right and left shoulders of the sows were assigned a score between 0 (normal) and 4 (lesion > 2.3 cm in diam.) on d 1 of the study and weekly thereafter throughout lactation. If a lesion developed, sows were randomly placed into 1 of 3 treatment groups. Groups consisted of a control group that received no treatment, a group that had a 0.2-cm thick, 60 x 60-cm, stainless steel plate attached to the bottom of the farrowing crate, and a group that had a 3.8-cm thick, 60 x 60-cm rubber mat attached to the bottom of the farrowing crate. Of the 310 sows involved in the study, 107 (34%) developed a lesion with a score of 3 or 4. Multivariate regression analysis identified body condition at weaning, flank-to-flank measurements at weaning, breed, parity, farrowing room section, and weaning weight of the litter as significantly associated with development of a shoulder lesion of score 3 or 4. The average number of days for the lesions to be completely resolved was 25 for sows receiving rubber mats, 32 for the controls, and 39 for the sows receiving stainless steel plates. Rubber mats attached to the bottom of the farrowing crates decreased the time required to heal the lesions when compared with controls. The low cost per mat (less than 0.90 dollars factoring in repeated use) makes it an economical and effective treatment.

Triple Reassortant H3N2 Influenza A Viruses, Canada, 2005

Since January 2005, H3N2 influenza viruses have been isolated from pigs and turkeys throughout Canada and from a swine farmer and pigs on the same farm in Ontario. These are human/classical swine/avian reassortants similar to viruses that emerged in US pigs in 1998 but with a distinct human-lineage neuraminidase gene.

American Ginseng From Five Different Sources Has Differential Effects On Postprandial Blood Glucose

We have previously demonstrated that, among 8 popular ginseng species, cultivated American ginseng (Panax quinquefolius) is one of the most efficacious in lowering postprandial blood glucose. It is not known, however, whether any other batch of cultivated American ginseng would replicate this finding. The present study aimed to assess the glycemia lowering effect of American ginseng from five Ontario farms with varying growing conditions in a controlled multiple cross-over intervention. 12 healthy individuals (5M:7F, age: 27± 2y, BMI: 24 ± 1 kg/m2) were tested on 6 separate occasions, after a 12h overnight fast. Each subject received 9g of American ginseng root from different farms, in random order, or a water control 40 min prior to a 75g oral glucose tolerance test. Venous blood samples were drawn prior to treatment intake and the 75 g glucose load and 15, 30, 45, 60, 90, 120 min after the glucose intake. Comparisons with control showed that ginseng from three farms significantly lowered blood glucose and area under the curve, farm A being the source of the most potent ginseng identified in this study. Overall, American ginseng reduces postprandial glycemia. However different batches do not consistently reproduce the identified glycemia lowering effect. Even among efficacious batches, differential glucose-lowering amplitudes are observed. These variable biologic responses might be explained through compositional differences due to various growing conditions of ginseng. This calls for further identification of the active glycemia-lowering components and subsequent ingredient-based standardization of ginseng.

Promotion of weed species diversity and reduction of weed seedbanks with conservation tillage and crop rotation

In a 6-yr study on four farms (36 fields) in Ontario, Canada, we tested the effects of tillage (moldboard, chisel plow, no tillage) and crop rotations (continuous corn, corn-soybean, corn-soybean-winter wheat) on emerged and seedbank weed species diversity and density. Aside from the imposed experimental treatments, all other management was generally consistent among farms. Tillage had the largest effect on weed diversity and density. No tillage promoted the highest weed species diversity, chisel plow was intermediate, and moldboard plow resulted in the lowest species diversity. These results are consistent with ecological succession theory. The increase in weed species diversity resulted from 20 species being associated with no tillage systems, 15 of which were winter annuals, biennials, or perennials. Emerged weed density was affected only by tillage. Over 6 yr, seedbank declined in no-tillage systems from 41,000 to 8,000 seeds m−3. Crop yields were not affected by tillage or crop rotation. In practical terms, reduced tillage in combination with a good crop rotation may reduce weed density and expenditures on weed management.

Greenhouse gas emissions from stored liquid swine manure in a cold climate

Current global warming has been linked to increases in greenhouse gas (GHG) concentrations. Animal manure is an important source of anthropogenic GHG, mostly of methane (CH 4) and nitrous oxide (N 2O). Country-specific emission estimates of these GHG can be obtained using IPCC 2000 guidelines, or suggested improvement, such as the USEPA approach for CH 4 emissions, which is based on monthly air temperature ( T air ). These approaches have not been validated against measured CH 4 and N 2O fluxes for liquid swine manure storage in cold climates due to the scarcity of year-round studies. A four-tower micrometeorological mass balance method was used at three swine farms (Arkell, Guelph, and Jarvis) in Ontario, Canada (annual T air <10 °C), from July 2000 to May 2002. Methane and N 2O concentrations were measured using two tunable diode laser trace gas analyzers, and manure temperature ( T man ), redox potential ( E h ) and composition were also measured. Dry matter content and E h between sites and seasons varied from 0.6% to 3%, and −232 and −333 mV, respectively. Annual T air was 8.4 °C, and T man was on average 4 °C warmer. Mean N 2O fluxes were not significantly different from zero, except for Jarvis with mean fluxes of 337.6 ng m −2 s −1 in summer and 101.8 ng m −2 s −1 in fall. Mean yearly N 2O emission was estimated as 3.6 g head −1 yr −1, and was lower than the IPCC-based emission factor (EF) of 17 g head −1 yr −1. Our data suggests that N 2O emissions from non-aerated liquid swine manure storage could be ignored in GHG inventories. Mean monthly CH 4 fluxes obtained from half-hourly data varied between 4.6×10 −3 and 1.05 mg m −2 s −1 (number of measurements per month=25–562). Measured CH 4 emissions from May to October were mostly larger, and from January to April were lower than values predicted using the USEPA approach. Use of T man improved monthly CH 4 emission prediction using the USEPA approach compared to T air with a lower limit of 7.5 °C ( r 2 = 0.64 vs. 0.355). The methane conversion factor derived from measured fluxes was 0.23, comparable to the USEPA derived values of 0.22–0.25, but much lower than the IPCC recommended value for cold climates (0.39).

A micrometeorological mass balance approach for greenhouse gas flux measurements from stored animal manure

Storage of animal manure is estimated to be a significant agricultural source of the greenhouse gases methane (CH 4) and nitrous oxide (N 2O). These estimates are, however, quite uncertain due to the lack of in situ measurements of fluxes. The micrometeorological mass balance method (MMB) is well suited for non-intrusive flux measurements from these sources. In this paper, we propose a four-tower MMB approach for simultaneously measuring CH 4 and N 2O fluxes from outdoor animal manure storage tanks. This approach was evaluated in studies at two commercial swine farms in Ontario, Canada, over 2 years. Each of the four air sampling towers used was designated as an upwind or downwind tower depending on wind direction. Mean CH 4 and N 2O concentration differences between upwind and downwind tower positions were measured simultaneously using two tunable diode laser trace gas analyzers and a 16-air intake sampling system. Tower azimuth and 1 min wind direction means were used to obtain mean half-hourly fetch (path of airflow travel over source). Mean concentration profiles showed the liquid manure storage tanks were significant sources of CH 4 but not N 2O. The presence of CH 4 sources in the area surrounding the manure storage tank affected background (or upwind tower) gas concentrations, and this effect was considered in flux calculations. Four sampling heights were sufficient to capture the profiles. Flux calculations were improved when the following filtering criteria were used to select data: wind veering within 30–90°, wind speed over 2 m s −1 at height 3.5 m, and restricting angles by 30° for tower designation. The simplest method for horizontal flux integration with height (rectangular method) yielded CH 4 flux means similar to the other methods evaluated (regression, interpolation, trapezoidal). The four-tower MMB approach allowed for flux measurements regardless of wind direction, and fluxes obtained were representative of contrasting areas within the storage tank, allowing for evaluation of the spatial heterogeneity of the source.

Herd Level Risk Factors for Non-infectious and Infectious causes of Lameness for Ontario Dairy Herds

Lameness is one of the most important issues facing the dairy industry, both in terms of production costs and public perception of dairy cow welfare. To assist bovine practitioners in making recommendations that reduce or prevent lameness, there is a need for knowledge about the prevalence of lameness and a more complete understanding of the factors that contribute to lameness in different North American management systems. The objective of this project was to determine the effect of selected risk factors on the prevalence of infectious and non-infectious claw lesions on dairy farms in Ontario.

Phenoxyacetic Acid Herbicide Exposure for Women on Ontario Farms

Women living and working on farms would be expected to have higher exposure to pesticides than the general nonoccupationally exposed population. Urinary concentrations of the herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and (4-chloro-2-methyl) phenoxyacetic acid (MCPA) were measured in 125 women living on farms in Ontario where these herbicides had recently been used for the first time that growing season. The women collected a spot urine void prior to the start of herbicide handling by spouses, followed by 2 consecutive 24-h urine samples. The pesticide applicator provided questionnaire data on pesticides that were used on the farm. Approximately 80% of the women had no detectable level of either herbicide in their urine. Geometric mean urinary concentrations of 2,4-D and MCPA in the d-2 samples were 0.7 µg/L. The responses to the questions on herbicide use on the farm were compared with urinary levels of the herbicide and the sensitivity for MCPA was determined to be 95–100%; however, the false positive rate for exposure was 70%. For 2,4-D, the sensitivity and specificity were approximately 70%, with a false positive rate of 30%. A simple question on whether the herbicide was used recently can accurately identify people who are likely not exposed; however, further research is required to be able to more validly predict those individuals who are exposed. Based on our study, it was concluded that exposure estimates based on questionnaire data alone may be fraught with uncertainties, which may differ depending on the particular pesticide of interest. This work does not necessarily reflect the views of Health Canada and no official endorsement should be inferred.

Indirect sources of herbicide exposure for families on Ontario farms

Although direct contact during mixing/loading, application or repair and clean-up is the major pathway by which individuals living on farms are exposed to herbicides, indirect sources such as contact with contaminated surfaces may also contribute. As part of a biomonitoring study to measure the nature and extent of exposure of farm families to herbicides, we attempted to identify potential indirect sources of exposure in a subset of 32 Ontario farms. Herbicide residues in drinking water samples as well as surface swipes of common surfaces within the home were measured and compared with urinary concentrations of the applicator, spouse and child. Residues of 2,4-dichlorophenoxyacetic acid (2,4-D) were measured on all surfaces that were tested, with the highest levels found on the washing machine knob and wash-up faucet within the home. Drinking water was not a significant source of exposure to 2,4-D for farm families. Urine samples of family members were weakly correlated with residues of 2,4-D measured on the exterior door knob. The applicators in our study, the most highly exposed subpopulation in our study group, had exposures that were less than one-third of the exposure on a daily, lifetime basis deemed to be safe by regulatory agencies in Canada and the United States. As 2,4-D residues were detected on surfaces in farm homes where 2,4-D was not reportedly used at that time, this suggests that 2,4-D applied during a previous season (or on a neighbouring farm) may be tracked into the home and persist on hard surfaces and be a chronic, albeit low level, source of exposure for family members. Pesticide applicators and their families should be counselled on hygienic practices (e.g. removing footware and washing soiled hands prior to entering the home) to reduce indirect sources of exposure. Journal of Exposure Science and Environmental Epidemiology (2006) 16, 98-104. doi:10.1038/sj.jea.7500441; published online 13 July 2005.

Unraveling the Voices and Identity of Farm Women

In this qualitative study I explored how rural farm women construct, negotiate, and perform gender identity in their everyday lives. To understand this process, 22 farm women located on family farms in Southwestern Ontario were interviewed. Differences were found between those women who were raised and socialized on farms and women who were born in the city. Women who worked off-farm had another experience when they returned to the farm from their workplace. Collectively the women took on the farmwork that was expected of them. They learned to adjust to the lifestyle and ways of farming. The ideology of agrarianism and separate spheres helped to delineate ways of being and doing that maintained their strong yet traditional and submissive sense of self.

Microbial Assessment of Irrigation Water Used for Production of Fruit and Vegetables in Ontario, Canada

Five hundred one irrigation water samples were collected from 27 irrigation water sources on 17 farms in southern Ontario, Canada, over a single irrigation season in 2002. The water samples were tested for the presence of the following bacterial water quality indicators: total coliform bacteria, fecal coliforms, Escherichia coli, and fecal streptococci. The median values per 100 ml of these indicators in the irrigation water samples were 3,000, 33, 15, and 1, respectively. Between 70.6 and 98.2% of irrigation water samples contained acceptable levels of fecal coliforms or E. coli, according to published irrigation water quality guidelines. Significant correlations (P < 0.05) were observed between the concentrations of different bacterial indicators and the degree of recent precipitation and concentrations of total coliforms and fecal streptococci. With the exception of fecal streptococci, which increased in number toward the end of the study, none of the indicators displayed a significant trend over the course of the season, as determined by linear regression analysis of indicator concentrations over time (P > 0.05).

Methicillin-resistantStaphylococcus aureusin Horses and Horse Personnel, 2000–2002

Methicillin-resistant Staphylococcus aureus (MRSA) infection was identified in 2 horses treated at a veterinary hospital in 2000, prompting a study of colonization rates of horses and associated persons. Seventy-nine horses and 27 persons colonized or infected with MRSA were identified from October 2000 to November 2002; most isolations occurred in a 3-month period in 2002. Twenty-seven (34%) of the equine isolates were from the veterinary hospital, while 41 (51%) were from 1 thoroughbred farm in Ontario. Seventeen (63%) of 27 human isolates were from the veterinary hospital, and 8 (30%) were from the thoroughbred farm. Thirteen (16%) horses and 1 (4%) person were clinically infected. Ninety-six percent of equine and 93% of human isolates were subtypes of Canadian epidemic MRSA-5, spa type 7 and possessed SCCmecIV. All tested isolates from clinical infections were negative for the Panton-Valentine leukocidin genes. Equine MRSA infection may be an important emerging zoonotic and veterinary disease.

Spatial Variability of Soil Test Phosphorus, Potassium, and pH of Ontario Soils

Grid soil sampling is typically used for establishing management zones for site‐specific application of nutrients. The geostatistical procedures used to estimate values between sample locations require samples to be taken close enough to together that they are correlated to one another. An evaluation of the scale of variability of soil test P (STP), soil test K (STK), and soil pH for Ontario soils was conducted using autocorrelation analysis of 23 Ontario farm fields, which were grid‐sampled using a 30‐m spacing. The results of the autocorrelation analysis indicated that 13 of the 23 farm fields would require a grid spacing of less than 30 m to adequately assess their spatial variability. For only one site was the commonly used 100‐m grid spacing adequate for the assessment of the spatial patterns of STP and STK. Further analysis using F tests compared the residuals from three gridding procedures (kriging, inverse distance, and nearest neighbor) using 60‐ and 90‐m grid data to that of the residuals using the field mean soil test value. In most cases, soil test variation maps based on 60‐ or 90‐m grid soil samples did not result in an increased ability to predict the soil test level at a given location in the field. It was concluded that a grid spacing of 30 m or less would be required to adequately assess the spatial variation of STP, STK, and soil pH. Sampling at this intensity would require approximately 11 times as many soil samples as the commonly used 100‐m grid, which is likely to make the cost prohibitive.

Community-associated methicillin-resistant Staphylococcus aureus in horses and humans who work with horses

To evaluate the prevalence of nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) in horses and horse personnel. Prospective prevalence study. 972 horses and 107 personnel from equine farms in Ontario, Canada and New York state. Nasal swab specimens were collected from horses and humans on farms with (targeted surveillance) and without (nontargeted surveillance) a history of MRSA colonization or infection in horses during the preceding year. Selective culture for MRSA was performed. Isolates were typed via pulsed-field gel electrophoresis, and antibiograms were determined. MRSA was isolated from 46 of 972 (4.7%) horses (0/581 via nontargeted surveillance and 46/391 [12%] via targeted surveillance). Similarly, MRSA was isolated from 14 of 107 (13%) humans (2/41 [5%] from nontargeted surveillance and 12/66 [18%] from targeted surveillance). All isolates were subtypes of Canadian epidemic MRSA-5, an uncommon strain in humans. All isolates were resistant to at least 1 antimicrobial class in addition to beta-lactams. On all farms with colonized horses, at least 1 human was colonized with an indistinguishable subtype. For horses, residing on a farm that housed > 20 horses was the only factor significantly associated with MRSA colonization. For humans, regular contact with > 20 horses was the only identified risk factor. Results confirm a reservoir of colonized horses on a variety of farms in Ontario and New York and provide evidence that 1 MRSA strain is predominantly involved in MRSA colonization in horses and humans that work with horses.

And on that farm he had a wife: Ontario Farm Women and Feminism, 1900-1970 (review)

Reviewed by: And on that farm he had a wife: Ontario Farm Women and Feminism, 1900-1970 E.A. (Nora) Cebotarev And on that farm he had a wife: Ontario Farm Women and Feminism, 1900-1970. Monda Halpern. Montreal and Kingston: McGill-Queen's University Press, 2001. Pp. viii, 240. $70.00 This book is a welcome addition to the rather scarce literature on Ontario farm women. It makes a double contribution to our understanding of Ontario farm women's lives during almost an entire century. It shows the crucial roles farm women and their organizations have played in this period and it elucidates the ideology of social feminism ( SF) that informed women's lives in the home and on the farm, and their political activism in rural communities and beyond. This is a rich and solidly researched book and is a pleasure to read. In her main argument Halpern juxtaposes social feminism to Equity Feminism ( EF), to show farm women's progressiveness and agency and to dispel accusations of conservatism. She does this with rich documentation and numerous quotes that testify to farm women's incisive perceptiveness of their essential but subordinate position in the farm family and about their social reformist missions in the rural community. Halpern also shows the misgivings farm women had about the androcentricism [End Page 608] of rural culture. The study is set in the evolving socio-political and economic environment of Ontario and reflects the changes in farm, home, and women's ideology for the past century. The book is composed of seven chapters. In the first chapter Halpern explains her reasons for undertaking this research and presents an excellent theoretical discussion of her framework. The bases of SF, the notions of 'separate spheres' and 'women's specificity' emerge clearly in her discussion. The origins, history, and essence of SF are traced, and voices of critics and detractors are also included. The second chapter provides and excellent description of farm women's everyday life in patriarchal farm families. The mental health consequences of drudgery and large workloads in home and farm are brought to light. Chapter three documents farm women's awareness of the essential nature of their work, the unfairness of its undervaluation and invisibility, and the resentment they felt because priority was given to modernize the barn before the home. In the fourth chapter Halpern presents the history and evolution of home economics, as an example of SF thinking and practice. The pioneering work of Adelaide Hoodless is also described, with her organization of the Women's Institutes ( WI), culminating with the founding of the Macdonald Institute at the University of Guelph in 1903, offering farm daughters college degrees in practical household skills, lending a sense of professionalism to homemaking. Here Halpern also points out the rich contributions they made to the improvement of family life and farm women's status and self-esteem. Chapter five examines the WI as a successful social movement and farm women's organization, which indeed it was, considering the international influence of the WI in promoting farm women's organizations throughout the world. Farm women's weak support for women's suffrage and WI's longevity are seen as proof of farm women's aversion to EF. The longevity of Women's Institutesis compared with the rapid and successful emergence and equally fast demise of the United Farm Women of Ontario ( UFWO) in the interwar years. Here, I think, Halpern underestimates the importance to WI's success of the government's financial and legitimizing support, and WI's less adversarial and demanding political stance than that of the UFWOs. Further, Halpern describes the transformation of the WI's goals, away from enhancing family life to support for broader causes, such as the war efforts, and branching out into issues of community and policy reform. Here, says Halpern, is the progressive and radical aspect of SF and of farm women's political activism. It aimed to change the 'public sphere' by infusing it with superior feminine values and morals, thereby transforming society for the better. [End Page 609] Chapter six focuses on the drastic socio-economic and technological changes affecting farming in the years after...

Filth fly parasitoids on dairy farms in Ontario and Quebec, Canada

AbstractHymenopterous parasitoids of filth flies (Diptera: Muscidae) were surveyed during 2 years on dairy farms in Ontario and Quebec near Ottawa, Ontario, using freeze-killed sentinel house fly (Musca domestica L.) pupae and naturally occurring fly pupae collected on site. Musca domestica and Stomoxys calcitrans (L.) (stable fly) represented 98.3% of the natural fly hosts from which parasitoids emerged. Muscidifurax raptor Girault et Saunders, Nasonia vitripennis Walker, Pachycrepoideus vindemiae (Rondani), Spalangia cameroni Perkins, S. nigra Latreille, Trichomalopsis viridescens (Walsh), and Urolepis rufipes (Ashmead) (Pteromalidae) were recovered from both sentinel and natural fly pupae. Another eight species, S. drosophilae Ashmead, S. endius Walker, S. haematobiae Ashmead, S. nigroaenea Curtis, S. subpunctata Förster, Trichomalopsis dubia (Ashmead) (Pteromalidae), Aphaereta pallipes (Say) (Braconidae), and Phygadeuon ?fumator Gravenhörst (Ichneumonidae), were recovered only from natural pupae. Over the 2 years, M. raptor comprised 90.7% of emerged parasitoids from sentinel pupae but only 17.0% of emerged parasitoids from natural pupae. From natural pupae, S. cameroni, S. nigra, and S. nigroaenea collectively comprised 60.3% of emerged parasitoids; P. ?fumator comprised 13.5% and the remaining nine species 9.2%. The recoveries of S. endius and S. nigroaenea represent new distribution records for Canada, and several new host records are identified based on structure of the host fly puparium. The parasitoid fauna is compared with that known for western Canada, and recommendations are made for both regions concerning potential natural enemy enhancement for filth fly control.

Farm children's exposure to herbicides: comparison of biomonitoring and questionnaire data.

Pesticide exposure has been associated with various childhood cancers. However, most studies rely on questionnaires, with few using biologic measures of dose. This study was designed to measure herbicide exposure directly in children of farm applicators, and to compare these results with exposure imputed from questionnaire information. Two consecutive 24-hour urine samples were collected from 92 children of Ontario farm applicators who used the herbicides 2,4-D (2,4-dichlorophenoxyacetic acid) or MCPA (4-chloro-2-methylphenoxyacetic acid) for the first time during 1996. The farm applicator completed questionnaires describing his pesticide-handling practices as well as the child's location during the various stages of handling these pesticides. Approximately 30% of the children on farms using these herbicides had detectable concentrations in their urine, with maximum values of 100 microg/L for 2,4-D and 45 microg/L for MCPA. Children with higher levels were more likely to be boys and to have parents who also had higher mean urinary concentrations. The sensitivity and specificity of a simple indicator of use were 47% and 72%, respectively, for 2,4-D, and 91% and 30%, respectively, for MCPA, using the biomonitoring data as the gold standard. Information on living on a farm, or on living on a farm where a specific pesticide is used, is not enough to classify children's exposures. Given this potential for misclassification, we urge incorporation of biomonitoring studies in subsets of children at least to estimate the extent of misclassification.

Stress on the farm and its association with injury.

The objectives of this study were to examine associations between perceived psychosocial stress and farm injury among men and women in Ontario, Canada. Cross-sectional data from the Ontario Farm Family Health Study were used to investigate perceived levels of stress, farm injuries and their interrelationships. Age-standardized rates of injury were 13.3/100/year and 3.8/100/year for men and women, respectively. The most common types of injury were strains/sprains/torn ligaments and cuts/lacerations. Approximately 18% of men and 11% of women reported that their lives were "very stressful." Common sources of stress were money worries and feeling overworked. The risk for farm injury increased with level of stress. For men, the adjusted odds ratios for injury were: 1.00 (referent), 1.02 (95% CI: 0.72, 1.42), and 1.61 (95% CI: 1.08, 2.41)for lowest to highest stress levels, respectively. For women, adjusted odds ratios were: 1.00 (referent), 1.43 (95% CI: 0.83, 2.47), and 2.73 (95% CI: 1.38, 5.39). These risks were especially pronounced among women who were not employed off the farm. This study represents a novel quantitative analysis examining associations between perceived psychological stress and farm injury. Future research should investigate these associations in other farm populations, confirm their temporal directions, and further explore the effect of gender on the strength of these associations.