Propanil (3,4-dichloropropionanilide) particulate concentrations within and near the residences of families living adjacent to aerially sprayed rice fields.

Propanil is widely used as a postemergence herbicide in rice. Because it is typically applied aerially, there is a potential for propanil to drift into and around homes of those living adjacent to rice fields. Propanil has been shown to be immunotoxic in rodent models. The objective of this study was to measure the levels of propanil to which families living adjacent to aerially sprayed rice fields may be exposed. Air levels were sampled by actively and passively collecting propanil in and around the homes of volunteer families living in close proximity to rice fields sprayed with propanil. Homes ranged from 73 m to 113 m from treated rice fields. Sampling was conducted in the home, adjacent to the home (within 5 m of the home), 30 m from the home, and at the edge of the rice field. Concentrations were determined via gas chromatography/mass spectroscopy. Propanil levels adjacent to the homes ranged from nondetectable to 1,106.4 microg per 400 cm2 collection surface (2.0 microg detection limit). Wind direction and wind velocity were the primary determinants of propanil drift. At sites where the prevailing wind was blowing away from the home, no propanil was detected except at the edge of the field. Distance from the edge of the rice field also influenced the amount of drift with higher levels measured at 30 m from the house than adjacent to the house. No propanil vapor was detected on absorbent media sampled in and around the homes. The results indicate that individuals living adjacent to rice fields aerially sprayed with propanil are potentially exposed to variable amounts of propanil, and wind speed and direction are the most important factors that influence the concentration of aerially applied pesticide.

Stability of Selected Pesticides on Solid-Phase Extraction Disks.

The storage stability of 2,4-D (2,4-dichlorophenoxy acetic acid), triclopyr ([(3,5,6-trichloro-2-pyridinyl) oxy] acetic acid), carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate), molinate (S-ethyl hexahydro-1 H-azepine-1-carbothioate), and thiobencarb (S-[(4-chlorophenyl) methyl] diethylcarbamothioate) on C18 solid-phase extraction (SPE) disks was determined under three temperature regimes. Water was fortified with either mixtures of the five pesticides at 20 µg L-1 of each pesticide or with methanol. Storage treatments included storage in water at 4°C, or the analytes were extracted onto the SPE disks and stored at 4°C, -20°C, or 4°C for 1 d followed by -20°C for the remaining storage period. Residue analyses were conducted after 0, 3, 30, 90, and 180 d of storage. All pesticides evaluated were more stable when stored on the disks vs. cold storage in water. Carbofuran was the least stable of the pesticides evaluated with losses ranging from 13 to 100% depending on storage period. The pesticides were most stable on the disks at temperature regimes that included -20°C with losses of ≤20% for 2,4-D, triclopyr, molinate, and thiobencarb for storage periods of 180 d. Storage of the same pesticides in water at 4°C resulted in losses of 25 to 35%.

Measurements of year-long exposure to tree nursery workers using multiple pesticides.

A year-long nurseryworker pesticide exposure study was designed to measure and evaluate the exposure occurring to workers who had the potential for simultaneous exposure to multiple pesticides. This four-State study was conducted in five nurseries (four USDA Forest Service and one State) involved in conifer seedling production. Primary comparisons were made among nursery workers in the Pacific northwest and south central United States. Worker exposure was assessed by using patches attached to clothing, handrinse samples and urine excreted from potentially exposed workers. In addition, dislodgeable residue in rinsate from a water wash of pesticide-treated seedlings was also evaluated. Four different groups of field workers, designated as applicators, weeders, scouts and packers, were included. The pesticide absorbed dose, assessed by urine analysis of pesticide metabolites and the deposition of pesticide on patches attached to the clothing of field workers, was monitored as they performed their duties under normal conditions (e.g., typical clothing, pesticide application). Monitoring was performed for the 14 different pesticides which were used in these nurseries. Seven pesticides were studied in more detail using biological monitoring. For these compounds, metabolites known to be excreted in the urine of exposed humans or other mammals were used to estimate the dose of pesticide absorbed by the exposed workers. The highest percentage of positive samples came from dislodgeable residue samples (8.3%) followed by patch samples (3.2%), handrinse (2.9%), and urine samples (1.3%). To summarize the conclusions from the urinary excretion data, 12 of the 73 nursery workers in the study received a low absorbed dose of pesticide. Biological monitoring revealed that three pesticides (benomyl, bifenox and carbaryl) were found in the urine of some of the workers. Of the 3,134 urine samples analyzed there were 42 positive; 11 urine samples were positive for benomyl, while bifenox was responsible for 13 positives and carbaryl accounted for the remaining 18. The 12-week continuous monitoring of urine showed that metabolites of these materials were rapidly excreted; thus, no build-up in the body is anticipated. Margins of Safety (MOS) calculations were made to provide an assessment of the significance of the exposure. Based on the low frequency of positive urine samples in the study, the low levels of metabolites when they were found, their apparent rapid excretion rate and the No Observed Effect Level (NOEL) data, furnished from other sources, nursery worker exposure to pesticides in these conifer nurseries is below health threatening levels.

Biomarkers of pesticide exposure.

Incorporation of biomarkers in studies of occupational exposure hazards is now recognized as a highly useful adjunct to the surrogate measures employed in the past, for example, time worked, ambient air data, interview responses. Application to studies of workers potentially exposed to pesticides has barely begun and provides many challenges to chemist/epidemiologist teams. This review indicates several excellent studies employing multiple-exposure measures to document the validity of specific biomarkers for particular exposure situations. In general, exposure reflected by urinary assays of specific pesticides is a low percentage of that indicated by dermal or breathing zone measures. Markers for many of the pesticides in current usage have yet to be developed and validated, and information on population variability is generally lacking for existing markers. The challenge provided by the complexity of multiple, and often unknown, exposures to individuals in pesticide environments has begun to be addressed employing cytogenetic or urinary measures that attempt to integrate these complex exposures. The lack of data regarding sensitivity and specificity of biomarkers, especially in complex exposure situations, is a major problem that perhaps will best be addressed by studies combining nonspecific measures with specific ones, utilizing stored sample banks created for that purpose. Expanding the repertoire of available biomarkers of pesticide exposure and employing multiple ones in well-designed study protocols will provide critical tools in the evaluation of pesticide safety and design of appropriate measures to minimize adverse exposures. Ironically, one of the problems that biological markers of exposure can help overcome, reliance on poorly measured ambient exposure data, hampers the evaluation of the markers themselves. Therefore, the combination of in vitro, animal, and human data will give the best picture of a marker's performance. (Wilcosky 1990).

Conifer seedling nursery worker exposure to glyphosate.

This study addresses the measurements of glyphosate exposure received by 14 workers employed at two tree nurseries. The applicators, weeders, and scouts monitored all wore normal work clothing, which for applicators was a protective suit, rubber gloves and boots. Measurements were made of the glyphosate that was dislodged from conifer seedlings during water rinses taken twice weekly from May through August. Only 1 of these 78 dislodgeable residue samples were positive for glyphosate. Nine cotton gauze patches were attached to the clothing of each worker one day per week during this same period. Hand washes were taken on the same day that patches were worn. Most patches and hand washes from applicators and weeders contained measurable amounts of glyphosate. Analyses of individual patches showed that the body portions receiving the highest exposure were ankles and thighs. For scouts only 1 of 23 hand washes contained glyphosate. To provide a measure of the exposure occurring via all exposure routes (dermal, ingestion, and inhalation) an analysis was made of the total urine excreted. For most workers a daily total urine collection was made for 12 consecutive weeks. Urine analysis, the biological monitoring tool used to assess the total amount absorbed via all avenues, did not reveal any positive samples. The lower limit of method validation for glyphosate in the urine samples was 0.01 micrograms/ml. High rainfall, or irrigation as needed, in conjunction with normal field dissipation avenues and worker training were cited as contributing factors for the low amounts of glyphosate exposure found.(ABSTRACT TRUNCATED AT 250 WORDS)

Progress in pesticide exposure studies and future concerns.

A campaign to educate the public regarding the merits of pesticides is necessary if we are to overcome the widespread poor image of pesticides that exists in society today. A comparison of biological monitoring and measurements of pesticide deposition on patches suggests that since only the absorbed dose has any potential for adverse health effects if forced to choose one technique over the other, more emphasis should be placed on biological monitoring. Controlled human pesticide exposure and dermal absorption studies establishing pharmacokinetic data are necessary if scientists and regulatory officials are expected to make knowledgeable worker safety recommendations pertaining to the pesticides being used today. Worker exposure can continue beyond the application day if pesticide-contaminated boots or gloves are used later. Excretion rate of 2,4-D in human urine was not affected by the presence of picloram in the application mixture. Margins of safety guidelines are highly dependent on adoption of appropriate no observed effect levels (NOEL).