Continuing Impacts of Selective Inhibition on Bacterial and Fungal Communities in an Agricultural Soil.

Selective inhibition (SI) has been routinely used to differentiate the contributions of bacteria and fungi to soil ecological processes. SI experiments typically measured rapid responses within hours since the addition of inhibitor, but the long-term effects of selective biocides on microbial community composition and function were largely unknown. In this study, a microcosm experiment was performed with an agricultural soil to explore the effectiveness of two bactericides (bronopol, streptomycin) and two fungicides (cycloheximide, captan), which were applied at two different concentrations (2 and 10 mg g-1). The microcosms were incubated for 6 weeks. A radiolabeled substrate, [1,2,3,4,4a,9a-14C] anthracene, was spiked to all microcosms, and the derived CO2 was monitored during the incubation. The abundance and composition of bacteria and fungi were assessed by qPCR and Miseq sequencing of ribosomal rRNA genes. It was demonstrated that only 2 mg g-1 bronopol and cycloheximide significantly changed the bacteria to fungi ratio without apparent non-target inhibition on the abundances; however, community shifts were observed in all treatments after 6 weeks incubation. The enrichment of specific taxa implicated a selection of resistant or adapted microbes by these biocides. Mineralization of anthracene was continuingly suppressed in all SI microcosms, which may result in biased estimate of bacterial and fungal contributions to pollutant degradation. These findings highlight the risks of long-term application of selective inhibition, and a preliminary assessment of biocide selection and concentration is highly recommended.

Provoking factors, including chemicals, in Dutch patients with vitiligo.

BACKGROUND: In vitiligo, many provoking factors have been described, but epidemiological data, especially on the role of contact with chemicals, are scarce. OBJECTIVE: To obtain an insight into the patient-reported factors provoking vitiligo, including contact with chemicals. METHODS: A retrospective cohort study was conducted on all 1264 patients with vitiligo who visited the Netherlands Institute for Pigment disorders from January 2003 to December 2007. Patients for whom an exogenous provoking factor was recorded were sent a questionnaire. Subsequently, patients who mentioned a chemical provoking factor were contacted to elucidate the alleged causal relationship between exposure to the chemical and the onset of vitiligo. RESULTS: A total of 300 out of the 1264 patients indicated that provoking factors had played a role in their disease. Two hundred and forty-six patients were sent a questionnaire, which was returned by 177 (response rate of 72%). Emotional stress was indicated as a provoking factor in 98 patients (55.4%), 51 patients (28.8%) recorded sunburn, 34 patients (19.2%) recorded mechanical factors and 20 patients (11.3%) other factors. Of 29 patients (16.4%) who indicated a chemical factor, a presumed causal relationship could be corroborated in four. The chemicals involved were para-tertiary butylphenol (n = 2), captan (n = 1) and diphencyprone (n = 1). CONCLUSION: The majority of the patients with vitiligo from this study did not mention provoking factors, but the ones who did point to emotional stress in more than half of the cases. Of the 29 patients who assigned chemical provoking factors, solvents were mainly indicated. However, a presumed relationship with the chemical could be corroborated in only four patients.

Multiple myeloma and exposure to pesticides: a Canadian case-control study.

The objective of this study was to investigate the putative associations of specific pesticides with multiple myeloma. A matched, population-based, case-control study was conducted among men residing in six Canadian provinces (Quebec, Ontario, Manitoba, Saskatchewan, Alberta, and British Columbia). Data were collected on 342 multiple myelome cases and 1506 age and province of residence matched controls. Data were collected by mailed questionnaires to capture demographic characteristics, antecedent medical history, detailed lifetime occupational history, smoking history, family history of cancer, and exposure to broadly characterized pesticides at home, work, and practicing hobbies. Details of pesticide exposures were collected by telephone interview for those who reported 10 hours or more per year of exposure. Exposure to pesticides grouped into major chemical classes resulted in increased risk being detected only for carbamate insecticides [odds ratio (OR) and 95% confidence interval (CI) 1.90 (1.11, 3.27) adjusted for potential confounders]. An exposure to fungicide captan [2.35 (1.03, 5.35)] was positively associated with the incidence of multiple myeloma. While an exposure to carbaryl [1.89 (0.98, 3.67)] was associated with the incidence of multiple myelome with borderline significance. The authors further suggest that certain pesticide exposures may have a role in multiple myeloma etiology, and identify specific factors warranting investigation in other populations.

Cancer incidence among pesticide applicators exposed to captan in the Agricultural Health Study.

OBJECTIVE: Captan is a widely used antifungal pesticide whose potential to cause cancer in humans is uncertain. METHODS: We evaluated the incidence of cancer among pesticide applicators exposed to captan in the Agricultural Health Study. Detailed information on pesticide exposure and lifestyle factors was obtained from self-administered enrollment questionnaires completed between 1993 and 1997. RESULTS: Of the 48,986 applicators enrolled 4,383 (9%) had applied captan. Median follow-up time was 9.14 years. Poisson regression analysis was used to estimate relative risks (RR) for cancer subtypes by tertiles of captan exposure. We investigated risk for all cancers combined and sites of cancer for which at least 15 cases occurred among captan-exposed applicators. These sites included cancers of the prostate, lung, and colon, blood-related cancers, and colorectal cancers. During follow-up 2,912 incident primary cases of cancer were identified. No association between the highest tertile of captan exposure (>67.375 intensity-weighted days) and development of all cancers (RR = 0.89; 95% CI, 0.71-1.13) or cancer of any specific site was observed. CONCLUSION: Although our study is limited by low numbers of observed cancer cases and follow-up time of 9.14 years, it does not provide evidence of an increased risk for the development of cancer at the investigated sites.

Human intake fractions of pesticides via greenhouse tomato consumption: comparing model estimates with measurements for Captan.

Human intake due to pesticide residues in food commodities can be much higher than those related to water consumption and air inhalation, stressing the importance to correctly estimate pesticide uptake into plants and predict subsequent intake by humans. We calculated the human intake fraction of captan via tomato consumption taking into account the time between pesticide application and harvest, the time between harvest and consumption, the absorption of spray deposit on plant surfaces, transfer properties through the cuticle, degradation inside the plant and loss due to food processing. Human population intake fractions due to ingestion were calculated for complete, washed and peeled tomatoes. The calculated intake fractions were compared with measurements derived from an experimental setup in a Mediterranean greenhouse. The fraction of captan applied in the greenhouse as plant treatment that eventually is ingested by the human population is on average 10(-2)-10(-5), depending on the time between pesticide application and ingestion of tomatoes and the processing step considered. Model and experimentally derived intake fractions deviated less than a factor of 2 for complete and washed tomatoes and a factor of 3 for peeled tomatoes. Intake fractions due to air inhalation and consumption of drinking water are expected to be significantly lower (5-9 orders of magnitude) than those induced by the intake of tomatoes in this case study.

Improved estimation of dermal pesticide dose to agricultural workers upon reentry.

Agricultural workers reentering fields after pesticide application to engage in hand labor activities are subject to potentially significant dermal exposures to residues on foliage and in soil. Environmental Protection Agency (EPA) guidelines for assessment of post-application exposures were originally described in the 1984 Pesticide Assessment Guidelines Subdivision K which is currently undergoing revision. A successor document will eventually appear as Series 875, Group B Postapplication Exposure Monitoring Test Guidelines. Regulatory protocols found in these documents utilize dislodgeable foliar residues, foliage-to-human-transfer coefficients, and duration of activity to estimate exposure. Dermal absorption factors are then used to estimate dose. However, the experiments from which absorption factors are derived typically involve constant or nearly constant exposures which are not consistent with assumed field exposure conditions. This can lead to inconsistent interpretation and questionable dose estimates. An AFL-CIO challenge to procedures used by EPA to estimate the dose of the fungicide captan [N-trichloromethylthio-4-cyclohexene-1,2-dicarboximide] to strawberry harvesters, which elicited a response from EPA, provides a useful opportunity for examination of the derivation and use of absorption factors. An improved, but still relatively simple, method for dermal dose estimation featuring explicit treatment of the time dependence of absorption has been developed. A benefit of the proposed method is capability for consideration of the effect of delay in post-shift washing on dose.

Exposure to fungicides in fruit growing: re-entry time as a predictor for dermal exposure.

As part of a European Concerted Action on Male Reproduction Capability an exposure assessment survey was conducted among seasonal workers in the fruit growing sector in the Netherlands. Dermal exposure to the fungicides captan and tolylfluanid was measured using cotton gloves (12 persons) and skin pads on several body parts (12 persons). In addition, a set of exposure data was used from a study conducted recently among Dutch fruit growers. For harvesting activities, re-entry time appeared to be an important determinant of dermal exposure to captan and tolyfluanid. Explained variance of regression models was moderate to high (range 0.30-0.87). For captan, calculated half-life times from the most recent exposure survey were lower (glove data: 5 days; pad data: 6 days) compared with half-life times based on the previously conducted study (11 days). Possible explanations for the discrepancy are discussed. For tolylfluanid, estimated half-life times during harvesting were 2 and 3 days, based on pad and glove data, respectively. Prediction of captan exposure during other crop activities appeared to be far more difficult (explained variance equal to 0.06), although the estimated half-life time was comparable with that for harvesting. The data suggest that re-entry time gives useful information to group workers in broad exposure categories. Nonetheless, it was concluded that large studies are needed to evaluate the importance of re-entry time in more detail.

[Occupational eczema in gardeners and greenhouse workers in the county of Funen]. / Erhvervsbetinget eksem hos fynske gartnere og gartnerimedhjaelpere.

The aims of the study were to assess the prevalence of and association between occupational dermatitis and possible risk factors in gardeners and greenhouse workers living on Funen, describe the distribution of different types of eczema and detect the allergens most commonly involved. A cross-sectional study, based on a postal questionnaire and subsequent patch testing of selected persons was carried out in 1958 gardeners. The response rate was 84.6%, and among 250 persons patch tested the most frequently sensitizing occupational allergens were plants of the Compositae family and the fungicide captan. Allergic occupational contact dermatitis was suspected in 43 persons (17%). Irritant eczemas outnumbered allergic eczemas and both were most often caused by plants. The lifetime prevalence of occupational dermatitis was 19.6%. Occupational mucosal symptoms, working with Compositae and training as a gardener in females were significantly associated with an increased prevalence of occupational eczema, whereas sex, age and personal atopy seemed to be of less importance.

Occupational contact dermatitis among New Zealand farmers.

Forty-six farmers were patch tested to determine whether their dermatitis was secondary to an occupational allergen. Twenty-eight had a positive patch test of which 23 were thought relevant (definite or probable). In 20 of these cases, the allergen(s) was considered to be work related (define or probable). The common allergens were pesticides (N-(1,1,2,2-tetrachloroethylthio) -4-cyclohexene-1,2-dicarboximide (captafol), ethylenebis (dithiocarbamato) manganese (maneb) and copper sulfate), rubber compounds (N-isopropyl-N-phenyl-4-phenylenediamine (IPPD) and 4-phenylene diamine base) and sunscreen chemicals.

Development of a field bioassay for the side effects of pesticides on decomposition.

A method has been developed for assessing the side effects of fungicides on decomposition using litterbags. Twenty dried leaf disks of Chinese cabbage, Brassica oleracea, were placed in litterbags (20 x 20 cm) made of nylon fabric (25 microns mesh). The litterbags were laid in a treated plot and 5, 10, 20, and > 200 m from the treated plot and covered with 1 cm of standard soil. After 1 week, the dry weight of the leaf disks was determined. In an iterative procedure the method was optimized and significant differences of 5% in decomposition rate between litterbags were found using the final method presented here. In and around agriculturally managed plots, negative effects on decomposition of two fungicides could be traced. Effects on decomposition were found after application of captan (in fruit, 1.5 kg a.i./ha) and maneb (in potatoes, 3 kg a.i./ha) up to 10 m from the treated plot, at moderate wind speeds (3-5 m/s). In one case the concentration of captan in the soil covering the litterbags was measured. A negative correlation was established between captan concentration and decomposition. These experiments were repeated in an experimental plot under more controlled conditions with respect to the amount and time of application. The results of the field experiments could not be reproduced on the experimental plot. Additional experiments with soil fungi in agar again demonstrated a significant effect of exposure to captan, however. Given the results, the method using litterbags requires further development before a standard field trial can be designed. Given the knowledge gained with respect to the key factors involved, a bioassay using soil fungi seems to have high potential, however.

Occupational dermatitis in Danish gardeners and greenhouse workers (II). Etiological factors.

The aim of the study was to assess the distribution of different types of occupational eczema among employees in floristry and detect the allergens most commonly involved. Based on a postal questionnaire, 253 gardeners and greenhouse workers with occupational skin symptoms and 52 randomly-selected without symptoms were examined and patch tested. Routine tests comprised the standard series, the Compositae mix, feverfew and 3 fungicides, with additional testing based on case records. 184 persons from the symptom group and 1 from the random group had occupational eczema. Irritant occupational contact eczema was suspected in 150 persons (59%). Nevertheless, 48% of the 250 persons patch tested had at least 1 positive reaction, most frequently to nickel, followed by Compositae which were positive in 25 cases (10%), of whom 24 were possibly occupationally sensitized. 13 persons from symptom group had positive reactions to fungicides. Occupational allergic eczema was suspected in 43 persons (17%), most often caused by plants belonging to the Compositae, Geraniaceae and Liliaceae families. New plant sensitizers were Exacum affine and Begonia lorraine. Exposure to specific plant species seemed to be the most important eliciting factors in both allergic and irritant occupational dermatitis in floristry, and preventive measures should include reduction of contact with plants.

Occupational asthma in a pesticides manufacturing worker.

A 34-year-old chemical manufacturing worker had new onset of work-related asthma after several years of exposure to the fungicide, captafol. On specific bronchial challenge testing, he demonstrated a marked and persistent fall in FEV1. Cessation of exposure resulted in improved symptoms and pulmonary function. The delay in symptoms after several years of workplace exposure and the dual reaction demonstrated on specific bronchial challenge testing suggest sensitization to some component of technical-grade captafol, but an IgE response was not detected.

Evidence of reduced poly-B-hydroxybutyrate biosynthesis in free-living nitrogen-fixing bacteria, Azotobacter chroococcum, following acquired resistance to the fungicide captan.

Some biological activities of Azotobacter chroococcum, strain Azcap 1, (spontaneous mutant, captan resistant up to 300 micrograms/ml) were assayed on RM medium with and without the presence of the fungicide. Comparisons were also carried out with Az. chroococcum sensitive strains Azwt, Azcan 10 and 14. The hydrolysis of captan, incorporated in agar plates of RM at 100 micrograms/ml, was rapid, since on 4-day plates, no effect was found on the strain Azwt, while on freshly prepared ones its growth was completely blocked. As for Azcap 1, grown on RM only, the behaviour was similar to that of sensitive strains, whereas when grown on captan the results of experiments showed: (i) a lag of approximately 12 h to reach the maximum nitrogen-fixing activity; (ii) delay of 12-24 h in the full consumption of glucose present in the medium, although the invertase activity did not present differences; (iii) high ATP culture content during the 50 h of the experiment; (iv) approximately 6-10-fold lower production of PHB (poly-B-hydroxybutyrate); (v) lack of typical encystment phase, for the tested 96 h and reduced viability in developing colonies on agar RM medium. In contrast, when captan was added to cultural medium at sublethal concentration, 50 micrograms/ml for sensitive strain Azwt and 200 micrograms/ml for Azcap 1, the amount of glutathione produced (to remove the fungicide toxicity) was several times higher for the former.

Prevalence of adverse reproductive outcomes in a population occupationally exposed to pesticides in Colombia.

A prevalence survey of adverse reproductive outcomes was carried out in a population of 8867 persons (2951 men and 5916 women) who had been working in the floriculture industry in the Bogotá area of Colombia for at least six months. These workers were exposed to 127 different types of pesticides. The prevalence rates for abortion, prematurity, stillbirths, and malformations were estimated for pregnancies occurring among the female workers and the wives of the male workers before and after they started working in floriculture, and these rates were related to various degrees of exposure. A moderate increase in the prevalence of abortion, prematurity, and congenital malformations was detected for pregnancies occurring after the start of work in floriculture.