Personal exposure assessment of pesticides in residents: The association between hand wipes and urinary biomarkers.

BACKGROUND: Residential exposure to pesticides may occur via inhalation of airborne pesticides, direct skin contacts with pesticide-contaminated surfaces, and consumption of food containing pesticide residues. The aim was to study the association of dermal exposure to pesticides between the use and non-use periods, between farmer and non-farmer families and between dermal exposure and the excretion of metabolites from urine in residents living close to treated agricultural fields. METHODS: In total, 112 hand wipes and 206 spot urine samples were collected from 16 farmer and 38 non-farmer participants living within 50 m from an agricultural field in the Netherlands. The study took place from May 2016 to December 2017 during the use as well as the non-use periods of pesticides. Hand wipes were analysed for the parent compound and urines samples for the corresponding urinary metabolite of five applied pesticides: asulam, carbendazim (applied as thiophanate-methyl), chlorpropham, prochloraz and tebuconazole. Questionnaire data was used to study potential determinants of occurrence and levels of pesticides in hand wipes according to univariate and multivariate analysis. RESULTS: Carbendazim and tebuconazole concentrations in hand wipes were statistically significantly higher in the pesticide-use period compared to the non-use period. In addition, especially during the use periods, concentrations were statistically significantly higher in farmer families compared to non-farmer families. For asulam, chlorpropham and prochloraz, the frequency of non-detects was too high (57-85%) to be included in this analysis. The carbendazim contents in urine samples and hand wipes were correlated on the first and second day after taking the hand wipe, whereas chlorpropham was only observed to be related on the second day following the spray event. CONCLUSIONS: Concentrations in hand wipes were overall higher in pesticide use periods compared to non-use periods and higher in farmer families compared to non-farmer families. Only for carbendazim a strong correlation between concentrations in hand wipes and its main metabolite in urine was observed, indicating dermal exposure via contaminated indoor surfaces. We expect this to be related to the lower vapour pressure and longer environmental lifetime of carbendazim compared to the other pesticides studies.

Comparison of low cost measurement techniques for long-term monitoring of atmospheric ammonia.

An inter-comparison of techniques for long-term sampling of atmospheric ammonia (NH3) was conducted with a view to establishing a national network with > 50 sites. Key requirements were for: a low cost system, simplicity and durability to enable a postal exchange with local site operators, a precision of < +/- 20% for monthly sampling at expected NH3 concentrations of 1-2 micrograms m-3, a detection limit sufficient to resolve the small NH3 concentrations (< 0.2 microgram m-3) expected in remote parts of the UK, and a quantitative means to establish quality control. Five sampling methods were compared: A, a commercially available membrane diffusion tube (exposed in triplicate), with membranes removed immediately after sampling; B, the above method, with the membranes left in place until analysis; C, open-ended diffusion tubes (exposed with 4 replicates); D, a new active sampling diffusion denuder system; and E, an active sampling bubbler system. Method D consisted of two 0.1 m acid coated glass denuders in series with sampling at approximately 0.3 l min-1. These methods were deployed at 6 locations in the UK and the Netherlands and compared against reference estimates. Method D was the most precise and sensitive of the techniques compared, with a detection limit of < 0.1 microgram m-3. The bubbler provided a less precise estimate of NH3 concentration, and also suffered several practical drawbacks. The diffusion tubes were found to correlate with the reference at high concentrations (> 3 micrograms m-3), but were less precise and overestimated NH3 at smaller concentrations. Of the passive methods, A was the most precise and C the least precise. On the basis of the results, method D has been implemented in the national network, together with application of method A to explore spatial variability in regions with expected high NH3 concentrations.

Measurement of the dry deposition flux of NH3 on to coniferous forest.

The dry deposition flux of NH3 to coniferous forest was determined by the micrometeorological gradient method using a 36 m high tower. Aerodynamic characteristics of the site were studied, using a second tower erected in the forest 100 m from the first. Fluxes and gradients of heat and momentum measured on both towers indicated a fairly homogeneous turbulent flow field over the studied area of the forest. Site specific flux profile functions for heat were derived from continuous measurements of turbulent fluxes and gradients. These functions were used to derive fluxes from the observed gradients of NH3. In total, eighty 90-min NH3 flux runs were performed. The results indicate a strong nonstomatal uptake of NH3 by the forest. A representative dry deposition velocity for NH3 of 3.6 cm(-1) s was derived. The annual average flux was roughly estimated to be equivalent to 50 kg N ha(-1) yr, significantly higher than the critical load for coniferous forest.

The exchange of nitric oxide, nitrogen dioxide and ozone between pasture and the atmosphere.

Fluxes of NO, NO2 and O3 were determined over a drained marshland pasture in south-east England by using flux-gradient techniques. Nitric oxide was found to be emitted at rates of up to 40 ng m(-2) s(-1), the rate of emission being related to the magnitude of the eddy diffusivity. Nitrogen dioxide deposited at rates of up to 90 ng m(-2) s(-1) under the control of stomatal resistance, a clear diurnal cycle being observed. Minimum canopy resistance was of the order of 80 s m(-1). Ozone deposition was also controlled by stomatal resistance, the minimum canopy resistance being around 100 s m(-1) and fluxes reaching a maximum of 220 ng m(-2) s(-1). Corrections made to NO and NO2 fluxes to compensate for chemical reactions showed flux divergences of the order of 30% for NO and NO2, but these were not statistically significantly different from the measured fluxes. The pasture was found to be a net sink for nitrogen in the form of NOx.