Occurrence and bioavailability of pyrethroids in a mixed land use watershed.

The shift in land use patterns within many urban areas has the potential to influence the magnitude and nature of nonpoint-source pollution. The presence of pyrethroid insecticides in urban surface streams is of particular concern due to the broad spectrum toxicity of pyrethroids to aquatic organisms and the widespread use of pyrethroid products for agricultural and urban pest control. Sediment samples were collected throughout a mixed land use watershed in southern California during two sampling periods and analyzed for a suite of pyrethroids. Bifenthrin and fenpropathrin were found most frequently in the sediment samples, with the highest concentrations associated with sites adjacent to large commercial nurseries. Sediments from residential areas or residential-commercial mixed areas had fewer detections and significantly lower concentrations than the nursery runoff sediments. No apparent difference was found between wet and dry season concentrations, which may be attributed to the fact that the lack of flow under dry weather conditions rendered pyrethroid residues immobile. Organic carbon-normalized sediment concentrations were poorly correlated with the freely dissolved pore water concentrations measured by solid phase microextraction (SPME), suggesting factors other than sediment organic carbon content should be considered when relating concentrations to potential toxicities.

Aggressive interactions between Solenopsis invicta and Linepithema humile (Hymenoptera: Formicidae) under laboratory conditions.

The Argentine ant, Linepithema humile (Mayr), and the red imported fire ant, Solenopsis invicta Buren, are natural agonists in their country of origin. Since the first report of L. humile in California in 1907 its range expanded statewide, displacing native ant species wherever it spread. Since the discovery of established populations of S. invicta in southern California in 1998, it has been restricted to discrete areas of southern California. However, as these discrete populations expand, they are encountering large populations of L. humile, which are effective competitors for available resources and are particularly aggressive in their encounters with other ant species such as S. invicta. Most Dolichoderine ants such as L. humile do not prefer to forage on baits made with defatted corn grit and soybean oil typically used in red imported fire ant control programs. Applications of these baits in areas where distributions of these species overlap might selectively affect populations of S. invicta and give L. humile a competitive advantage. Three laboratory experiments were conducted to determine the competitive outcomes between S. invicta pitted against L. humile: 1) agonistic behavior of workers in small arenas, 2) colony interactions with different population ratios, and 3) the effects of pyriproxyfen on the competitiveness of S. invicta against L. humile. Populations of S. invicta consisting of major workers killed more L. humile than did minors or a mixture of majors and minors. When paired against L. humile colonies consisting of 1,100 workers, colonies consisting of 38 S. invicta workers were easily defeated by L. humile. Colonies consisting of 450 S. invicta workers plugged their nest entrances, but they were ultimately defeated by L. humile after 13 d. The S. invicta colonies consisting of 1,100 workers took control of the bridge connecting the colonies, invaded the L. humile colony, killed the Argentine ant queens, and removed their brood. Pyriproxyfen-treated fire ant workers took significantly longer to chase the Argentine ants from a connecting bridge than did untreated fire ants. Thus, fire ant baits may have long-term effects on intercolonial aggression between S. invicta and L. humile, especially when Argentine ant populations are high in the summer.

Distribution and persistence of pyrethroids in runoff sediments.

Pyrethroids are commonly used insecticides in both agricultural and urban environments. Recent studies showed that surface runoff facilitated transport of pyrethroids to surface streams, probably by sediment movement. Sediment contamination by pyrethroids is of concern due to their wide-spectrum aquatic toxicity. In this study, we characterized the spatial distribution and persistence of bifenthrin [BF; (2-methyl(1,1'-biphenyl)-3-yl)methyl 3-(2-chloro-3,3,3-trifluoro-1-propenyl)-2,2-dimethylcyclopropanecarboxylate] and permethrin [PM; 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylic acid (3-phenoxyphenyl)methyl ester] in the sediment along a 260-m runoff path. Residues of BF and PM were significantly enriched in the eroded sediment, and the magnitude of enrichment was proportional to the downstream distance. At 145 m from the sedimentation pond, BF was enriched by >25 times, while PM isomers were enriched by >3.5 times. Pesticide enrichment along the runoff path coincided with enrichment of organic carbon and clay fractions in the sediment, as well as increases in adsorption coefficient K(d), suggesting that the runoff flow caused selective transport of organic matter and chemical-rich fine particles. Long persistence was observed for BF under both aerobic and anaerobic conditions, and the half-life ranged from 8 to 17 mo at 20 degrees C. The long persistence was probably caused by the strong pesticide adsorption to the solid phase. The significant enrichment, along with the prolonged persistence, suggests that movement of pyrethroids to the surface water may be caused predominantly by the chemically rich fine particles. It is therefore important to understand the fate of sediment-borne pyrethroids and devise mitigation strategies to reduce offsite movement of fine sediment.

Recovery of synthetic pyrethroids in water samples during storage and extraction.

Monitoring for synthetic pyrethroids in surface water at the sub-parts per billion level requires reproducible sampling and analytical methods. We studied the recovery of bifenthrin, permethrin, and deltamethrin in water during storage in glass containers and extraction using solid-phase membranes. In solid-free water, the concentration of all compounds quickly decreased and then remained constant at 58-72% of the initial concentration, likely due to adsorption to the glass surface. The recovery was enhanced in runoff samples that contained suspended solids, which was attributed to the association of pesticides to the suspended solids. However, the greatest loss occurred when runoff samples were not agitated before extraction, and the loss was largely caused by the exclusion of the suspended solids from the aqueous phase. Nearly 100% extraction recoveries were obtained when C(8) or C(18) membranes were used for extracting runoff samples. Adsorption to glass surfaces and suspended solids can result in substantial underestimation of pyrethroid concentrations or biological activity and therefore should be considered when designing monitoring protocols.

An instrument to measure musculoskeletal symptoms among immigrant Hispanic farmworkers: validation in the nursery industry.

We report on the construction and psychometrics of a survey measure of musculoskeletal symptomatology for use with Spanish-speaking immigrant farmworkers. Survey development included focus groups with workers, forward and backward translations, and pilot testing. The final survey includes a body diagram and items about symptom severity, frequency, and duration and about self-treatment, medical care, and job tasks. We report on the initial test of the survey with 213 commercial nursery workers in Southern California. Fifty-five percent of the workers reported pain, with 30% reporting back pain, 21% reporting upper extremity pain, 19% reporting lower extremity pain, and 10% reporting neck and shoulder pain. A composite symptom score exhibited acceptable test-retest reliability (r = 0.41, p < 0.01) over the annual agricultural cycle. Greater symptomatology was associated with greater frequency of self-treatment (r = 0.42, p < 0.01), seeking professional health care (t = 2.49, p < 0.05), and exposure to high-risk jobs (OR = 2.1, p < 0.05, CI = 1.0 to 4.4), supporting the validity of composite score.

Effects of thiabendazole on the kidneys of ICR mice.

The effects of thiabendazole (TBZ) on the kidneys of male and female Crj:CD-1 (ICR) mice were investigated. The mice were given 0, 250 or 500 mg TBZ/kg body weight/day by gavage (using olive oil as a vehicle) for 1, 3, 5 or 7 days. The 24-hr urine volumes of treated mice were increased, significantly so in male mice given the high dose of TBZ. Protein was present in the urine of both control and treated mice throughout the experiment but electrophoresis of the protein showed the presence of a relatively high-molecular-weight protein in the urine of the treated mice. Levels of serum urea nitrogen were decreased in treated mice, but serum creatinine levels did not differ from those of controls. Relative kidney weights tended to be dose-dependently increased in comparison with the controls. Pathological examination showed that after one dose (at either level) the kidneys of males and females were swollen and white maculae were present. Microscopic examination revealed dilation of the proximal, distal and collecting tubules with flattening and degeneration of the tubular epithelium. Tubular dilation was severe in high-dose male mice. These histological changes paralleled the alterations in the 24-hr urine volume. These data suggested that the increased urine volume may be caused primarily by the prevention of reabsorption of water in the distal and collecting tubules. Electron microscopy revealed the flattening of foot processes of podocytes and oedematous changes in the mesangium of glomeruli in TBZ-treated mice. We conclude that TBZ given by gavage in olive oil affects the kidneys of ICR mice.

The metabolic profile of sodium o-phenylphenate after subchronic oral administration to rats.

We examined the metabolites of o-phenylphenol (OPP) in the urine of male and female rats dosed with 2% sodium o-phenylphenate (OPP-Na) in food from the age of 5 wk for 136 days. The urinary metabolites of OPP-Na produced during the 24 hr after OPP-Na feeding accounted for 55% of the dose in male rats and 40% in females. The main metabolites were OPP-glucuronide and 2,5-dihydroxybiphenyl (2,5-DHBP)-glucuronide. OPP metabolites in the free form accounted for only 1% of the total phenolic metabolites excreted. 2,5-DHBP was rapidly converted to the corresponding quinone in aqueous solvents but not in organic solvents. There was a clear sex difference in the proportions of urinary metabolites; the amount of 2,5-DHBP excreted by male rats in 24-hr urine was more than seven times that excreted by females. This result may be related to the finding that bladder tumours occur in male but not female rats fed OPP-Na in the diet.