Toxaphene Treatment Research Articles

Toxaphene-induced mouse liver tumorigenesis is mediated by the constitutive androstane receptor.

Toxaphene was shown to increase liver tumor incidence in B6C3F1 mice following chronic dietary exposure. Preliminary evidence supported a role for the constitutive androstane receptor (CAR) in the mode of action of toxaphene-induced mouse liver tumors. However, these results could not rule out a role for the pregnane X receptor (PXR) in liver tumor formation. To define further the nuclear receptors involved in this study, we utilized CAR, PXR and PXR/CAR knockout mice (CAR-/- , PXR-/- and PXR-/- /CAR-/- ) along with the wild-type C57BL/6. In this study CAR-responsive genes Cyp3a11 and Cyp2b10 were induced in the liver of C57BL/6 (wild-type) mice by toxaphene (30-570-fold) (at the carcinogenic dose 320 ppm) and phenobarbital (positive control) (16-420-fold) following 14 days' dietary treatment. In contrast, in CAR-/- mice, no induction of these genes was seen following treatment with either chemical. Cyp3a11 and Cyp2b10 were also induced in PXR-/- mice with toxaphene and phenobarbital but were not changed in treated PXR-/- /CAR-/- mice. Similarly, induction of liver pentoxyresorufin-O-deethylase (CAR activation) activity by toxaphene and phenobarbital was absent in CAR-/- and PXR-/- /CAR-/- mice treated with phenobarbital or toxaphene. Ethoxyresorufin-O-deethylase (EROD, represents aryl hydrocarbon receptor activation) activity in CAR-/- mice treated with toxaphene or phenobarbital was increased compared with untreated control, but lower overall in activity in comparison to the wild-type mouse. Liver EROD activity was also induced by both phenobarbital and toxaphene in the PXR-/- mice but not in the PXR-/- /CAR-/- mice. Toxaphene treatment increased 7-benzyloxyquinoline activity (a marker for PXR activation) in a similar pattern to that seen with pentoxyresorufin-O-deethylase. These observations indicate that EROD and PXR activation are evidence, as expected, of secondary overlap to primary CAR receptor activation. Together, these results definitively show that activation of the CAR nuclear receptor is the mode of action of toxaphene-induced mouse liver tumors. Copyright © 2017 John Wiley & Sons, Ltd.

Mechanistic Investigation of Toxaphene Induced Mouse Liver Tumors.

Chronic exposure to toxaphene resulted in an increase in liver tumors in B6C3F1 mice. This study was performed to investigate the mode of action of toxaphene induced mouse liver tumors. Following an initial 14 day dietary dose range-finding study in male mice, a mechanistic study (0, 3, 32, and 320 ppm toxaphene in diet for 7, 14, and 28 days of treatment) was performed to examine the potential mechanisms of toxaphene induced mouse liver tumors. Toxaphene induced a significant increase in expression of constitutive androstane receptor (CAR) target genes (Cyp2b10, Cyp3a11) at 32 and 320 ppm toxaphene. aryl hydrocarbon receptor (AhR) target genes (Cyp1a1 and Cyp1a2) were slightly increased in expression at the highest toxaphene dose (320 ppm). No increase in peroxisome proliferator-activated receptor alpha activity or related genes was seen following toxaphene treatment. Lipid peroxidation was seen following treatment with 320 ppm toxaphene. These changes correlated with increases in hepatic DNA synthesis. To confirm the role of CAR in this mode of action, CAR knockout mice (CAR(-/-)) treated with toxaphene confirmed that the induction of CAR responsive genes seen in wild-type mice was abolished following treatment with toxaphene for 14 days. These findings, taken together with previously reported studies, support the mode of action of toxaphene induced mouse liver tumors is through a nongenotoxic mechanism involving primarily a CAR-mediated processes that results in an increase in cell proliferation in the liver, promotes the clonal expansion of preneoplastic lesions leading to adenoma formation.

Abstract 1698: Evaluation of pesticide involvement in breast cancer.

Abstract There is considerable evidence linking cumulative and sustained exposure to estrogens as a key promoter of breast tumor proliferation. Chemicals with estrogenic activity can bind to the estrogen receptor (ER) to affect downstream signaling of estrogen-responsive genes. Organochlorines are a class of chemical pesticides that can act as xenoestrogens to disrupt normal endocrine function. Mitochondria play a significant role in maintenance of energy regulation and cellular detoxification and mitochondrial DNA is sensitive to levels of estrogen. Some members of the Estrogen Related Receptor (ERR) family are known to interact with hypoxia inducible factors to modulate mitochondrial response through the mTOR pathway which is pivotal to cell homeostasis and cellular detoxification. This study investigates the link between two organochlorine pesticides, Methoxychlor and Toxaphene, and the cellular effects by examining the hypothesis that exposure induces differential molecular pathways. Two breast cancer cell lines, MCF-7 (ER+) and MDA-MB-231 (ER-), and a normal breast epithelial cell line MCF-10A are used as a model to evaluate the response to Methoxychlor and Toxaphene treatment. Cytotoxicity studies established different sensitivities of the two breast cancer cell lines to pesticides. MCF-7 was more sensitive to both pesticides, which supports the premise that organochlorines may be acting as endocrine disruptors. Furthermore, pesticide-resistant clones of MCF-7 and MDA-MB-231 were established and compared to their sensitive counterparts. RNA was collected from cells treated in a hypoxic environment, cells treated with a high dose pesticide, and cells that had a co-treatment of hypoxia and pesticide for evaluation of ERR, hypoxic factor expression, and markers of mTOR pathway. Flow cytometry, RT-PCR and immunoblotting demonstrated that treatment affected mitosis and mitochondrial function and we found that ERR and hypoxic factor expression changed in a similar manner suggesting a common mechanism by pesticide treatment or hypoxic conditions. These results provide a basis for understanding specific pesticide-induced molecular mechanisms and their possible relationship to ER+ and ER- mammary epithelial biology. Citation Format: Kathryn Patterson, Julie Hale, Jason Bush. Evaluation of pesticide involvement in breast cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1698. doi:10.1158/1538-7445.AM2013-1698

Liver proteome response of largemouth bass ( Micropterus salmoides) exposed to several environmental contaminants: Potential insights into biomarker development

Liver proteome response of largemouth bass ( Micropterus salmoides) exposed to environmental contaminants was analyzed to identify novel biomarkers of exposure. Adult male bass were exposed to cadmium chloride (CdCl 2), atrazine, PCB 126, phenanthrene, or toxaphene via intraperitoneal injection with target body burdens of 0.00067, 3.0, 2.5, 50, and 100 μg/g, respectively. After a 96 h exposure, hepatic proteins were separated with two-dimensional gel electrophoresis and differentially expressed proteins (vs. controls) recognized and identified with MALDI-TOF/TOF mass spectrometry. We identified, 30, 18, eight, 19, and five proteins as differentially expressed within the CdCl 2, atrazine, PCB 126, phenanthrene, and toxaphene treatments, respectively. Alterations were observed in the expression of proteins associated with cellular ion homeostasis (toxaphene), oxidative stress (phenanthrene, PCB 126), and energy production including glycolysis (CdCl 2, atrazine) and ATP synthesis (atrazine). This work supports the further evaluation of several of these proteins as biomarkers of contaminant exposure in fish.

Long‐term effects of toxaphene and depuration in lake trout and white sucker in a natural ecosystem

AbstractIndividuals from lake trout (Salvelinus namaycush) and white sucker (Catastomus commersoni) populations in a small lake located in the Experimental Lakes Area in northwestern Ontario, Canada, were treated with single intraperitoneal injections of toxaphene (7 μg/g or 3.5 μg/g) to better understand its potential effects on fish in their natural environment. Wild fish were captured, tagged, weighed, measured, injected with toxaphene, and released back into the lake. They were subsequently recaptured during spring (white sucker) and fall (lake trout) for the next 5 years. In years 2 and 3 following treatment, fish were spawned to assess reproductive success and survival of their offspring. Survival of adult lake trout and white sucker treated with toxaphene was decreased compared with controls. No changes in growth were evident in either species due to toxaphene treatment. No differences occurred in fertilization rate, total survival, or incidence of deformities in eggs and fry from female lake trout treated with toxaphene. Fertilization rates and survival to swim‐up of white sucker eggs and fry from females treated with toxaphene decreased relative to controls in both years. Maternal transfer of toxaphene from female to eggs was observed in both white sucker and lake trout; levels in eggs were much lower than in treated females but were still significantly higher than in controls. Residue analyses showed that depuration of toxaphene was slower than expected, with estimated half‐lives of 314 and 793 d in lake trout and white sucker, respectively.

Chlorobornanes in Sediments and Fish 30 Years after Toxaphene Treatment of Lakes

Chlorobornanes (CHBs) were isolated from recent and older sediments as well as from rainbow trout muscle in two prairie lakes that were treated with toxaphene as a pesticide in the early 1960s. Cored sediments representing the years of treatment (1961/1962) contained high concentrations of hepta-, octa-, and nonachlorobornanes (ΣCHBs, 1602 and 500 ng g -1 ) with a similar gas chromatographic peak pattern to technical toxaphene. In contrast, negative ion mass spectrometry confirmed that the near-surface sediments contained hexa- and heptachlorobornanes at levels not normally observed in environmental samples. This suggests that some of the original toxaphene mixture had been dechlorinated and was redistributed by porewater diffusion and/or sediment focusing. Analyses of fish revealed a toxaphene fingerprint similar to that of the dechlorinated material in sediments, suggesting that the chemical was both water soluble and bioavailable. Significant residual CHBs in surface sediments and in fish indicate that other toxaphene-treated lakes should be reexamined.

Fossil record of cladoceran and algal responses to fishery management practices

SUMMARY1. We hypothesized that the fishery management practices of toxaphene application and trout stocking would affect non‐target organisms in lakes. Because these practices were rarely monitored in the past, cladoceran and algal assemblages were quantified in sediment cores from two lakes treated 30+ years ago to determine the long‐term response of organisms near the base of the food chain.2. Chydorids were remarkably resistant over the short term (a few years) in both the oligotrophic and eutrophic lakes despite toxaphene treatments that extirpated native fish and other invertebrates. In the oligotrophic lake (Annette Lake), six chydorid taxa were less abundant in the years following treatment, although no loss of species richness was detected. In the eutrophic lake (Chatwin Lake), the dominant Chydorus cf. sphaericus declined coincident with toxaphene treatment, but longer‐term declines of all taxa were probably related to food web or other changes rather than to toxaphene toxicity. Cause and effect coupling was complicated by the fact that many chydorids were present at low concentrations in some pretreatment samples.3. The algal communities (as fossil pigments) responded to treatment differently in the two lakes. In the oligotrophic lake, planktonic diatoms, dinoflagellates and chlorophytes were replaced as dominants by deep‐water or benthic blooming cryptophytes, chrysophytes and cyanobacteria. This shift occurred along with increases in large daphnids and the ‘grazing indicator’, pheophorbide a. While both lakes appear to have had enhanced pigment preservation following treatment, the eutrophic lake encountered few long‐term changes in its fossil pigment assemblage. Redundancy analysis estimated that the presence or absence of stocked trout explained much of the variation in the algal assemblages, particularly in the oligotrophic lake.4. Toxaphene remained elevated in profundal sediments from these lakes 30 and 35 years after treatment.

Long-term Invertebrate Community Response to Toxaphene Treatment in Two Lakes: 50-yr Records Reconstructed from Lake Sediments

Analysis of sediment cores from two toxaphene-treated and one untreated lake basin demonstrates both the short-term effect of toxaphene applied in 1961–62 and the longer term effect of subsequent trout stocking on invertebrates. In Chatwin Lake (higher toxaphene concentration), planktonic cladocerans decreased in abundance, and dominance quickly changed from small- to large-bodied types. Bosmina was reduced by 88% at the time of toxaphene application and was eliminated during the 1970's as invertebrate predators like Chaoborus americanus increased in response to the poor survival of stocked fish. Short-term toxic effects were not detectable in cores from Peanut Lake (lower toxaphene concentration). In both treated lakes, large invertebrates became dominant with the absence of native fish and during trout stocking. Chaoborus spp. remained at low levels throughout the 1960's in both treated lakes compared with the untreated lake, possibly due to residual toxaphene toxicity and/or to predation by stocked fish. Toxicity to total chironomids was not detected, although genera-specific responses were not analysed. While the higher toxaphene dosage caused residual toxicity in Chatwin Lake for at least a decade, the manipulation of fish communities was primarily responsible for long-term changes in the invertebrates of both lakes.

Reconstructing the effect of toxaphene treatment and fish stocking on invertebrates in a western Canadian lake

Reconstructing the effect of toxaphene treatment and fish stocking on invertebrates in a western Canadian lake

SCE induction and cell-cycle delay by toxaphene

Toxaphene is genotoxic in mammalian cell systems and also inhibits cell replication. It was therefore used to investigate possible masking of SCE induction due to cell-cycle delay. In this study, toxaphene-treated Chinese hamster lung (Don) cells exhibited a dose-dependent decrease in cell-cycle progression compared with untreated cells. At high, nontoxic toxaphene levels (15 μg/ml), cell cycling also slowed as the toxaphee treatment time was increased. Toxaphene induced significantly higher numbers of SCEs in treated cells, demonsstrating a dose- and treatment time-relationship. Slopes of dose-response curves were 0.29, 0.43 and 0.77 SCE/μg toxaphen for 20.5 h, 24.5 h and 28.5 h incubation, respectively. There were no changes in sCE values in control cultures even when slower dividing cells were sampled e.g. at longer incubation times. Thus, higher SCE values in Chinese hamster cells were not associated per se with slower or more delayede cells. The results demonstrate that longer toxaphene treatment times were not necessary for obtaining sufficient harlequin-stained cells for SCE analysis, but that higher numbers of SCEs occurred in slower dividing cells, following prolonged incubation of cultures treated with toxaphene.

Reproduction study of toxaphene in the rat.

The purpose of the present study was to investigate in rats the reproductive effects of toxaphene, an insecticidal mixture which has been identified as a pollutant in the Great Lakes ecosystem. Groups of 30 female and 15 male weanling rats were given toxaphene in the diets at 0, 4.0, 20, 100 or 500 ppm in a 1 generation 2 litter reproduction study. Toxaphene treatment at the levels studied had no effects on the litter size, pup weight, fertility, or gestation and survival indices. Toxic effects in the parental rats included depressed weight gain, elevated serum cholesterol, and increased liver and kidney weight and hepatic microsomal enzyme activities. Most of these effects were associated only with 500 ppm toxaphene treatment. Treatment-related histological changes in the liver, thyroid and kidney of adult rats were observed at levels as low as 20 ppm. Based on the data presented, the no observable adverse effect dose of toxaphene was considered to be 4.0 ppm in the diet (0.29-0.38 mg/kg b.w./day depending on the amount of dietary intake).

Toxicity of toxaphene in the rat and beagle dog

Residues of the insecticidal mixture, toxaphene, have been found in Great Lakes fish. The purpose of the present study was to assess the subchronic toxicity of toxaphene in the rat and beagle dog. In the rat study, groups of 10 male and 10 female animals were fed diets containing 0, 4, 20, 100, or 500 ppm of the test compound for 13 weeks. No clinical signs of toxicity or spontaneous deaths were observed. Toxaphene treatment up to 500 ppm had no effects on weight gain or food consumption. The liver/body weight ratio and hepatic microsomal enzyme activities (phenobarbital type) were increased in both sexes fed 500 ppm of the test compound. Toxaphene at the highest dose also caused kidney enlargement in male but not in female rats. Dose-dependent histological changes were seen in the kidney, thyroid, and liver. Changes in the liver and thyroid were considered to be adaptative but the injury in the proximal tubules of the kidney was focally severe. Groups of six male and six female beagle dogs were fed toxaphene in gelatin capsules at 0, 0.2, 2.0, and 5.0 mg/kg body wt/day for 13 weeks. Food consumption and growth rate were not affected. All animals survived the entire treatment period. No clinical signs of toxicity were observed. The liver/body weight ratio and serum alkaline phosphatase were increased in dogs of both sexes fed 5.0 mg/kg. Mild to moderate dose-dependent histological changes were observed in the liver and thyroid. Toxaphene was accumulated in a dose-dependent manner in the fat and liver of dogs and rats. Based on the biochemical, histological, and residue data, it was concluded that the no-adverse-effect levels of the pesticide were 4.0 ppm (0.35 mg/kg) for the rat and 0.2 mg/kg for the dog.

Toxicity of Toxaphene in the Rat and Beagle Dog

Toxicity of Toxaphene in the Rat and Beagle Dog. CHU, I., VILLENEUVE, D.C, SUN, C., SECOURS, V., PROCTER, B., ARNOLD, E., CLEGG, D., REYNOLDS, L., AND VALLI, V.E. (1986). Fundam Appl. Toxicol. 7, 406-418. Residues of the insecticidal mixture, toxaphene, have been found in Great Lakes fish. The purpose of the present study was to assess the subchronic toxicity of toxaphene in the rat and beagle dog. In the rat study, groups of 10 male and 10 female animals were fed diets containing 0, 4, 20, 100, or 500 ppm of the test compound for 13 weeks. No clinical signs of toxicity or spontaneous deaths were observed. Toxaphene treatment up to 500 ppm had no effects on weight gain or food consumption. The liver/body weight ratio and hepatic microsomal enzyme activities (phenobarbital type) were increased in both sexes fed 500 ppm of the test compound. Toxaphene at the highest dose also caused kidney enlargement in male but not in female rats. Dose-dependent histological changes were seen in the kidney, thyroid, and liver. Changes in the liver and thyroid were considered to be adaptative but the injury in the proximal tubules of the kidney was focally severe. Groups of six male and six female beagle dogs were fed toxaphene in gelatin capsules at 0, 0.2, 2.0, and 5.0 mg/kg body wt/day for 13 weeks. Food consumption and growth rate were not affected. All animals survived the entire treatment period. No clinical signs of toxicity were observed. The liver/body weight ratio and serum alkaline phosphatase were increased in dogs of both sexes fed 5.0 mg/kg. Mild to moderate dose-dependent histological changes were observed in the liver and thyroid. Toxaphene was accumulated in a dose-dependent manner in the fat and liver of dogs and rats. Based on the biochemical, histological, and residue data, it was concluded that the no-adverse-effect levels of the pesticide were 4.0 ppm (0.35 mg/kg) for the rat and 0.2 mg/kg for the dog.

Adenosine triphosphatase activities in plasma liver membranes of rats treated with DDT and toxaphene.

The effect of exposure to chlorinated insecticides (DDT and toxaphene) on Na+,K+-ATPase, Mg2+-ATPase and Ca2+-ATPase activities of the plasma membrane of hepatocytes was determined. Acute treatment with DDT (200 mg per kg body weight) or toxaphene (110 mg per kg body weight) produced a significant decrease in Na+,K+-ATPase activity (80% and 85%, respectively) 24 h after treatment. DDT also produced a 30% decrease in Mg2+-ATPase and Ca2+-ATPase activity, but toxaphene treatment did not modify these enzymes. The effect of exposure to daily doses of DDT (30 mg per kg body weight) or toxaphene (16.5 mg per kg body weight) for a period of 3.5 months was also studied. Animals were sacrificed at 15-day intervals and results showed that Na+,K+-ATPase activity decreased 80% from the beginning of each treatment and the activity remained low throughout the treatment period. DDT, but not toxaphene, also led to a decrease in Mg2+-ATPase (20%) and Ca2+-ATPase (35%) activity. The low values observed from the beginning remained low throughout the treatment period. We believe that the general mechanism of ATPase inhibition by organochloride compounds could be the result of its interaction with membrane lipid components, although some differences could arise from differences in their spatial structure.

Susceptibility of Hereford cattle to sheep scab mites after recovery from psoroptic scabies.

Cattle scabies is caused by Psoroptes ovis (Hering), and Hereford cattle with a history of psoroptic scabies were as susceptible after reexposure to P. ovis as cattle exposed for the first time. The first reexposure of cattle to P. ovis after a 5-month latency period failed to cause psoroptic scabies. But a second reexposure resulted in body scab as extensive as that on naive cattle. Cattle free of P. ovis infestation for 4 months after toxaphene treatment developed scabies with as many mites as cattle exposed for the first time. Two cattle had severe scabies with many mites only while stanchioned and unable to groom. The data indicate that cattle after a 2- to 5-month period of latency or recovery from scabies because of pesticide treatment are as susceptible to P. ovis as cattle exposed for the first time. Self grooming behavior was the only factor which consistently limited the size of P. ovis populations.

Insecticide control of the Rocky Mountain wood tick on cattle in Wyoming.

Several insecticides were tested in 1963 and 1965 for the control of the Rocky Mountain wood tick Dermacentor andersoni Stiles on cattle in Wyoming. In the 1963 tests, toxaphene was more effective than dioxathion or coumaphos. In the 1965 tests there was no great difference between toxaphene, Ciodrin(R) and Compound 4072. In both tests, the concentrated treatments (5 & 10%) of toxaphene applied only to the sites normally infested by the ticks, e.g. the neck and brisket areas, caused a greater reduction in ticks after 2 weeks than that afforded after 1 week by conventional spray treatments. The residual toxicity of the concentrated toxaphene treatments was improved somewhat by the addition of certain extenders.

GROWTH-DILUTION AS A FACTOR IN THE DECLINE OF PESTICIDE RESIDUES ON ALFALFA-GRASS FORAGE

The persistence of endosulfan, Guthion, malathion, methoxychlor, Sevin, and toxaphene applied to alfalfa-grass forage for spittlebug control was studied by chemical analysis of deposits from application to harvest. Applications were made when the crop was 9 to 12 in. high. Malathion residues declined from 51 p.p.m. to trace amounts (0.26 p.p.m. or less) in 1 week, endosulfan from 18 to 0.36 p.p.m., and Sevin from 77 to 0.33 p.p.m. in 2 weeks, and Guthion from 74 to < 0.75 p.p.m. in 3 weeks. Methoxychlor and toxaphene treatments resulted in harvest residues from 1 to 9 p.p.m.To assess the rate at which the residues would have declined if diluted by growth alone, forage was cut from unit areas and weighed at each residue sampling time. At harvest the theoretical dilution by growth would have reduced the residues of methoxychlor and toxaphene to one-half their original level, whereas the actual residues were from one-fourteenth to one-eighth of the original deposits.

The Effectiveness of the Polyhedrosis Virus for Control of the Cabbage Looper, Trichoplusia ni

The polyhedrosis virus of the cabbage looper ( Trichoplusia ni (Hubner) was applied to cabbage on a schedule to determine the effects of various dosages per acre and time interval between application upon larval control. High dosages of polyhedra (9.5 × 1011 per acre) were more effective than low dosages (9.5 × 109 per acre) but all rates caused significant larval mortality. Weekly applications were more effective than biweekly applications. The latter treatments did not give significant control until 39 days after the initiation of the scheduled sprays. An increase in percentage control of each succeeding larval in star was noted. The weekly applications of 9.5 × 1011 polyhedra per acre averaged 0%, 36%, 66%, 79%, and 85% control of the first, second, third, fourth and fifth instars, respectively. Combinations of polyhedra with parathion and with toxaphene gave slight but significant increases in larval control over the materials used singly. Less worm damage was observed among plants treated with the polyhedra-parathion combination than with either one applied separately, but little difference occurred between the polyhedra-toxaphene combination treatment and toxaphene treatment.

Horn Fly Control by the Pour-on Technique Using Ruelene or Toxaphene1

Hereford yearling cattle naturally infested with horn flies ( Haematobia irritans (L.)) were treated by the pour-on technique or full-coverage sprays. Treatment was applied to 13 to 14 animals in each of six balanced, adjacent pastures. The animals in three pastures received one treatment, and those in the other three pastures received the alternate treatment. Pour-on treatments consisted of application of 100 ml. of concentrated emulsion applied to the back in each instance by means of a dipper. Comparisons were made of Ruelene® ( O -4- tert -butyl-2-chlorophenyl O -methyl methylphosphoramidate) as pour-on at 9.6 g./animal and US 0.25% spray, and of toxaphene as pour-on at 18 g./animal and as 0.5% spray. The pour-on procedure provided superior control in terms of absolute reduction of fly numbers and of length of time treatment remained effective. The toxaphene treatments were notably more effective than the Ruelene treatments by both application procedures. Erythrocyte cholinesterase levels were mildly depressed and were significantly lower among the Ruelene-pour-on animals than among the Ruelene-sprayed animals (82% vs. 88% of initial activity). No skin irritation was observed in any instance.

Control of Hippelates Gnats with Soil Treatments Using Oregano-chlorine Insecticides 1

The initial and long-term effectiveness of six organochlorine insecticides applied to soil were determined in the field against Hippelates gnats. The field trials were aimed mainly at controlling H. collusor (Townsend), the predominant species in California and the Southwest. Other species controlled were H. hermsi Saurosky, H. pusio Loew, and H. dorsalis Loew. But the latter two species maintain very low population densities in the Coachella Valley of southern California, where these investigations were carried on, and consequently are not a problem in that area. H. hermsi is not considered pestiferous. In a young citrus grove, aldrin, dieldrin, endrin, toxaphene, DDT, and DDT+toxaphene sprays were applied on the basis of equal cost per acre and effectiveness of these materials was ascertained over a period of 4 seasons. Excellent control of Hippelate collusor was obtained for 2 seasons with the DDT and DDT+toxaphene treatments, but the other materials provided only poor-to-fair control. In the third season, only the DDT treatment still gave significant reduction of the eye gnats. During the fourth season, DDT produced no appreciable control of the gnats. In other tests also, DDT sprays were effective against H. collusor , as well as against H. pusio and H. hermsi . In trials in two date gardens, endrin, applied at rates of 2 to 6 pounds per acre in both spray and granular forms, yielded erratic results and poor control of Hippelates collusor . Various concentrations of DDT granules produced poorer control of H. collusor and H. hermsi , 3 months after treatment than the sprays of approximately the same dosage. As the concentration of DDT in the formulation increased, the degree of control decreased. Shell Development Company compound SD-4402 (1,3,4,5,6,7,8,8 octachloro 3a,4,7,7a-tetrahydro-4,7-methanophthalan) applied as sprays (2 to 10 pounds per acre) gave good-to-excellent initial control of Hippelate collusor and H. hermsi but less control after 3 months. Only the 10-pounds-per-acre teatment yielded excellent control of H. collusor 3 months after application. Twelve months after treatment the 10-pounds-per-acre treatment produced excellent control of H. collusor . The 5-pounds-per-acre treatment also resulted in good control of this species 12 months after treatment. Both these dosages yielded moderate-to-good control of H. hermsi 12 months after treatment. Sixteen months after treatment the 10-pounds-per-acre rate of SD-4402 yielded excellent control of H. collusor and moderate control of H. hermsi . However, the emergence of both species was low and the residual activity of SD-4402 cannot be assessed clearly after this period.