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PubMed1991

Photosynthetic and stomatal conductance responses of Norway spruce and beech to ozone, acid mist and frost--a conceptual model.

Two-year-old beech and Norway spruce seedlings were exposed to a combination of ozone and acid mist treatments in open-top chambers in Scotland during the months of July through to September 1988. Replicate pairs of chambers received charcoal-filtered air (control), ozone-enriched air (140 nl ozone litre(-1)) or 140 nl ozone litre(-1) plus a synthetic acid mist (pH 2.5) composed of ammonium nitrate and sulphuric acid. Field measurements of assimilation and stomatal conductance were made during August. In addition, measurements of assimilation and conductance were made during September in the laboratory. Light response curves of assimilation and conductance were determined using a GENSTAT nonrectangular hyperbolic model. During February 1988/9 the Norway spruce were subject to a four day warming period at 12 degrees C and the light response of assimilation determined. The same plants were then subject to a 3-h night-time frost of -10 degrees C. The following day the time-course of the recovery of assimilation was determined. It was found that ozone fumigation did not influence the light response of assimilation of beech trees in the field, although stomatal conductance was reduced in the ozone-fumigated trees. The rate of light-saturated assimilation of Norway spruce was increased by ozone fumigation when measured in the field. Measurements of assimilation of Norway spruce made during the winter showed that prior to rewarming there was no difference in the rate of light-saturated assimilation for control and ozone-fumigated trees. However, the ozone plus acid mist-treated trees exhibited a significantly higher rate. The 4-day period of warming to 12 degrees C increased the rate of light-saturated assimilation in all treatments but only the ozone plus acid mist-treated trees showed a significant increase. Following a 3-h frost to -10 degrees C the control trees exhibited a reduction in the rate of light-saturated assimilation (Amax) to 80% of the pre-frost value. In comparison, following the frost, the ozone-fumigated trees showed an Amax of 74% of the pre-frost value. The ozone plus acid mist-treated trees showed an Amax of 64% of the pre-frost trees. The time taken for Amax to attain 50% of the pre-frost value increased from 30 min (control) to 85 min for ozone-fumigated trees to 190 min (ozone plus acid mist). These results are discussed in relation to the impact of mild, short-term frosts, which are known to occur with greater frequency than extreme, more catastrophic frost events. A simple conceptual framework is proposed to explain the variable results obtained in the literature with respect to the impact of ozone upon tree physiology.

Journal Article↗
PubMed1981

Stomatal Conductance and Sulfur Uptake of Five Clones of Populus tremuloides Exposed to Sulfur Dioxide.

Plants of five clones of Populus tremuloides Michx. were exposed to 0, 0.2 or 0.5 microliter per liter SO(2) for 8 hours in controlled environment chambers. In the absence of the pollutant, two pollution-resistant clones maintained consistently lower daytime diffusive conductance (LDC) than did a highly susceptible clone or two moderately resistant clones. Differences in LDC among the latter three clones were not significant. At 0.2 microliter per liter SO(2), LDC decreased in the susceptible clone after 8 hours fumigation while the LDC of the other clones was not affected. Fumigation with 0.5 microliter per liter SO(2) decreased LDC of all five clones during the fumigation. Rates of recovery following fumigation varied with the clone, but the LDC of all clones had returned to control values by the beginning of the night following fumigation. Night LDC was higher in the susceptible clone than in the other clones. Fumigation for 16 hours (14 hours day + 2 hours night) with 0.4 microliter per liter SO(2) decreased night LDC by half. Sulfur uptake studies generally confirmed the results of the conductance measurements. The results show that stomatal conductance is important in determining relative susceptibility of the clones to pollution stress.

Journal Article↗
PubMed2006

Evaluation of volatile low molecular weight insecticides using Drosophila melanogaster as a model.

Volatile insecticides, otherwise known as fumigants, have numerous uses in pest control and integrated pest management. Fumigants have been broadly applied in the protection of stored agricultural commodities and also in the elimination of structural pest infestations. However, fumigants have so far been mostly overlooked for use in management of public health pests such as flies and mosquitoes. This paper reports information on the development of a volatility bioassay for use in evaluating volatile insecticides against dipteran insects and on the use of this bioassay to compare the relative efficacy of 30 candidate compounds to Drosophila melanogaster Meig. The findings revealed seven highly effective insecticidal compounds, which include three heterobicyclics (menthofuran, thiophene and coumaran) and four formate esters [butyl, hexyl and heptyl formate and ethylene glycol diformate (EGDF)]. Ethyl formate, a compound previously identified as being a highly effective fumigant against coleopteran stored product pests, caused toxicity in Drosophila but was not as effective as other tested formates. Two volatile fumigant insecticides, dichlorvos (DDVP) and methyl isothiocyanate (MITC), were also tested as positive controls. Both of these volatile standards were significantly more toxic than the seven most effective of the novel compounds. Finally, regression analyses revealed that volatility is not entirely predictive of acute toxicity and that other structural features should be considered when designing and synthesizing volatile insecticidal compounds for future study.

Animals↗
PubMed2000

Activity of Plodia interpunctella (Lepidoptera: Pyralidae) in and around flour mills.

Studies were conducted at two flour mills where male Indian meal moths, Plodia interpunctella (Hübner), were captured using pheromone-baited traps. Objectives were to determine the distribution of male P. interpunctella at different locations in and around the mills throughout the season, and to monitor moth activity before and after one of the mills was fumigated with methyl bromide to assess efficacy of treatment. Commercially available sticky traps baited with the P. interpunctella sex pheromone were placed at various locations outside and within the larger of the two mills (mill 1). Moths were captured inside mill 1 after methyl bromide fumigations. The highest numbers of P. interpunctella were caught outside the facility and at ground floor locations near outside openings. Additional traps placed in the rooms above the concrete stored-wheat silos at mill 1 during the second year captured more moths than did traps within the mill's production and warehouse areas. In another study, moths were trapped at various distances from a smaller flour mill (mill 2) to determine the distribution of moths outdoors relative to the mill. There was a negative correlation between moth capture and distance from the facility, which suggested that moth activity was concentrated at or near the flour mill. The effectiveness of the methyl bromide fumigations in suppressing moth populations could not be assessed with certainty because moths captured after fumigation may have immigrated from outside through opened loading bay warehouse doors. This study documents high levels of P. interpunctella outdoors relative to those recorded inside a food processing facility. Potential for immigration of P. interpunctella into flour mills and other stored product facilities from other sources may be greater than previously recognized. Moth entry into a food processing facility after fumigation is a problem that should be addressed by pest managers.

Animals↗
PubMedDate not supplied

Effect of formulation on the behavior of 1,3-dichloropropene in soil.

The fumigant 1,3-dichloropropene (1,3-D) has been identified as a partial replacement for methyl bromide (CH3Br) in soil fumigation. 1,3-Dichloropropene is formulated for soil fumigation as Telone II (Dow AgroSciences, Indianapolis, IN) for shank application and as an emulsifiable concentrate (EC) (Telone EC or InLine; Dow AgroSciences) for drip application. This study investigated the effect of formulation on the phase partitioning, transformation rate, and volatilization of 1,3-D isomers. Air-water partitioning coefficients (K(H)) were slightly higher for Telone II than for Telone EC, presumably due to the higher apparent water solubility of the EC formulation. Sorption of 1,3-D isomers in two soils was not affected by formulation. Formulation had no significant effect on the rate of 1,3-D transformation in water or soil. In general, differences in the rate of 1,3-D transformation and phase partitioning due to formulation as Telone II or Telone EC were very small. Thus, the effect of formulation on 1,3-D fate may be ignored in transformation and phase partition of 1,3-D in water and soil. Packed soil columns without plastic tarp indicated that with relatively shallow subsurface (10 cm) drip application of Telone EC, emission of 1,3-D isomers was more rapid and produced greater maximum instantaneous flux than deeper (30 cm) shank injection of Telone II. Both application methods resulted in the same cumulative emissions for both isomers, 45% for (E)-1,3-D and approximately 50% for (Z)-1,3-D. These results suggest that for drip application of fumigants to be effective in reducing emissions, the fumigant must be applied at sufficient depths to prevent rapid volatilization from the soil surface if the water application rate does not sufficiently restrict vapor diffusion.

Agriculture↗
PubMed2005

Degradation of methyl isothiocyanate and chloropicrin in forest nursery soils.

Recent studies have observed enhanced degradation of methyl isothiocyanate (MITC) from repeated fumigation in agricultural soils. Little is known about fumigant degradation in forest and nursery soils. This study was conducted to determine degradation rates of MITC and chloropicrin (CP) in two forest soils and the impacts of nursery management on degradation of MITC and CP. The half-life values of MITC and CP were evaluated in the laboratory under isothermal conditions (22 +/- 2 degrees C). Three rates representing 0.5x, 1x, and 2x field application rates for each fumigant were used in laboratory incubations. Effect of microbial degradation was determined by conducting incubations with both fresh and sterilized soils. Soil moisture effects were also studied. There was no difference in MITC or CP degradation between fumigated and nonfumigated forest nursery soils. Soil sterilization and high soil moisture content (15% by wt.) reduced MITC and CP degradation. The degradation rates of MITC and CP varied with factors such as nursery history, fumigant application rates, and freshness of tested soils.

Biodegradation, Environmental↗
PubMed2007

Surface seals reduce 1,3-dichloropropene and chloropicrin emissions in field tests.

Reducing emissions is essential for minimizing the impact of soil fumigation on the environment. Water application to the soil surface (or water seal) has been demonstrated to reduce 1,3-dichloropropene (1,3-D) emissions in soil column tests. This study determined the effectiveness of water application to reduce emissions of 1,3-D and chloropicrin (CP) in comparison to other surface seals under field conditions. In a small-plot field trial on a Hanford sandy loam soil (coarse-loamy, mixed, superactive, nonacid, thermic Typic Xerorthents) in the San Joaquin Valley, CA. Telone C35 (61% 1,3-D and 35% CP) was shank-applied at a depth of 46 cm at a rate of 610 kg ha-1. Soil surface seal treatments included control (no tarp and no water application), standard high density polyethylene (HDPE) tarp over dry and pre-irrigated soil, virtually impermeable film (VIF) tarp, initial water application by sprinklers immediately following fumigation, and intermittent water applications after fumigation. The atmospheric emissions and gas-phase distribution of fumigants in soil profile were monitored for 9 d. Among the surface seals, VIF and HDPE tarp over dry soil resulted in the lowest and the highest total emission losses, respectively. Intermittent water applications reduced 1,3-D and CP emissions significantly more than HDPE tarp alone. The initial water application also reduced emission peak and delayed emission time. Pre-irrigated soil plus HDPE tarp reduced fumigant emissions similarly as the intermittent water applications and also yielded the highest surface soil temperature, which may improve overall soil pest control.

Allyl Compounds↗
PubMed1986

Suicide by exposure to sulfuryl fluoride.

The insecticide fumigant, sulfuryl fluoride, was used as an instrument of self destruction in at least two of the three fatal exposures detailed in this report. The autopsy findings, while nonspecific, have a confirmatory value. Toxicologic analysis should include a plasma and a urine fluoride level, since the toxic effects of exposure are probably related to this ion. Concentrations of fluoride in our cases were: 50.42 mg/L (Case 1) and 20 mg/L (Case 3). However, the values must be interpreted in light of all known information as a result of the paucity of reported cases of fatal sulfuryl fluoride exposures. The cases described provide a model for the investigation of tent fumigation deaths. Proper investigation of fumigant deaths requires knowledge of the insecticide, the fumigation procedure, and the implementation of warning devices. Guidelines are offered along with a procedural checklist for the investigation of tent fumigation deaths.

Adolescent↗
PubMedDate not supplied

United States Department of Agriculture-Agricultural Research Service stored-grain areawide integrated pest management program.

The USDA Agricultural Research Service (ARS) funded a demonstration project (1998-2002) for areawide IPM for stored wheat in Kansas and Oklahoma. This project was a collaboration of researchers at the ARS Grain Marketing and Production Research Center in Manhattan, Kansas, Kansas State University, and Oklahoma State University. The project utilized two elevator networks, one in each state, for a total of 28 grain elevators. These elevators stored approximately 31 million bushels of wheat, which is approximately 1.2% of the annual national production. Stored wheat was followed as it moved from farm to the country elevator and finally to the terminal elevator. During this study, thousands of grain samples were taken in concrete elevator silos. Wheat stored at elevators was frequently infested by several insect species, which sometimes reached high numbers and damaged the grain. Fumigation using aluminum phosphide pellets was the main method for managing these insect pests in elevators in the USA. Fumigation decisions tended to be based on past experience with controlling stored-grain insects, or were calendar based. Integrated pest management (IPM) requires sampling and risk benefit analysis. We found that the best sampling method for estimating insect density, without turning the grain from one bin to another, was the vacuum probe sampler. Decision support software, Stored Grain Advisor Pro (SGA Pro) was developed that interprets insect sampling data, and provides grain managers with a risk analysis report detailing which bins are at low, moderate or high risk for insect-caused economic losses. Insect density was predicted up to three months in the future based on current insect density, grain temperature and moisture. Because sampling costs money, there is a trade-off between frequency of sampling and the cost of fumigation. The insect growth model in SGA Pro reduces the need to sample as often, thereby making the program more cost-effective. SGA Pro was validated during the final year of the areawide program. Based on data from 533 bins, SGA Pro accurately predicted which bins were at low, moderate or high risk. Only in two out of 533 bins did SGA Pro incorrectly predict bins as being low risk and, in both cases, insect density was only high (> two insects kg(-1)) at the surface, which suggested recent immigration. SGA Pro is superior to calendar-based management because it ensures that grain is only treated when insect densities exceed economic thresholds (two insects kg(-1)). This approach will reduce the frequency of fumigation while maintaining high grain quality. Minimizing the use of fumigant improves worker safety and reduces both control costs and harm to the environment.

Agriculture↗
PubMed2004

Enrichment and molecular characterization of chloropicrin- and metam-sodium-degrading microbial communities.

Chloropicrin (CP) and metam sodium are commonly used as fumigants in agricultural soils in order to provide effective control of nematodes, soil-borne pathogens, and weeds in preparation for planting of high-value cash crops. Repeated application of these compounds to agricultural soils for many years may result in the enrichment of microorganisms capable of degrading them. In this study, a microcosm-enrichment approach was used to investigate bacterial populations that may be components of metam-sodium- and CP-degrading microorganisms in compost-amended soils. After 6 months incubation, with repeated application of metam sodium and CP, degradation was > or =70% faster in compost-manure-amended (CM) soil compared to < or =50% in the unamended soils. The accelerated fumigant degradation may have been due to the addition of compost or to the development of new microbial populations with enhanced degradation capacity. Denaturing gradient gel electrophoresis (DGGE) profiles of PCR-amplified regions of 16S rRNA genes were used to identify dominant bacterial populations responsible for the accelerated fumigant degradation. The DGGE results indicated that specific bacterial types had been enriched and these were similar to strains isolated from basal minimal media. Fragments from DGGE bands and colonies were cloned, sequenced, and compared with published 16S rRNA sequences. Cloned sequences were dominated by Pseudomonas, Bacillus, Arthrobacter, Mycobacterium and uncultured bacterial species. The addition of organic amendment to soil during fumigation practices has the potential to increase the diversity of different microbial species, thereby accelerating fumigant degradation and reducing atmospheric emissions.

Bacteria↗
PubMed1992

Influence of ozone air pollution on plant-herbivore interactions. Part 2: Effects of ozone on feeding preference, growth and consumption rates of monarch butterflies (Danaus plexippus).

Effects of ozone fumigation of Asclepias curassavica L. and A. syriaca L. on feeding preference, growth, development, and nutritional indices of monarch larvae were investigated in conjunction with changes in specific leaf metabolites. While foliar chemistry was quite variable, fumigation generally decreased sugars and proteins, and increased amino acids and phenolics in A. curassavica. Effects were similar in A. syriaca except that sugars were generally increased while amino acids were usually not affected. On A. curassavica, 3rd instar larvae preferred ozone-treated leaves while 4th instars showed no preference; conversely, on A. syriaca, 3rd instars showed no preference while 4th instars preferred control leaves. Relative growth rate and relative consumption rate of 5th instars were greater on fumigated plants of both species, but other nutritional indices were unaffected. Larvae developed more rapidly on intact fumigated plants of both species than on the respective controls. The results suggest that enhanced feeding stimulation may be the primary cause of the altered behavior and performance on ozone-fumigated plants.

Journal Article↗
PubMed2002

Impact of fungicides on active oxygen species and antioxidant enzymes in spring barley (Hordeum vulgare L.) exposed to ozone.

Two modern fungicides, a strobilurin, azoxystrobin (AZO), and a triazole, epoxiconazole (EPO), applied as foliar spray on spring barley (Hordeum vulgare L. cv. Scarlett) 3 days prior to fumigation with injurious doses of ozone (150-250 ppb; 5 days; 7 h/day) induced a 50-60% protection against ozone injury on leaves. Fungicide treatments of barley plants at growth stage (GS) 32 significantly increased the total leaf soluble protein content. Additionally, activities of the antioxidative enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate-peroxidase (APX) and glutathione reductase (GR) were increased by both fungicides at maximal rates of 16, 75, 51 and 144%, respectively. Guiacol-peroxidase (POX) activity was elevated by 50-110% only in AZO treated plants, while this effect was lacking after treatments with EPO. This coincided with elevated levels of hydrogen peroxide (H2O2) only in EPO and not in AZO treated plants. The enhancement of the plant antioxidative system by the two fungicides significantly and considerably reduced the level of superoxide (O2*-) in leaves. Fumigation of barley plants for 4 days with non-injurious ozone doses (120-150 ppb, 7 h/day) markedly and immediately stimulated O2*- accumulation in leaves, while H2O2 was increased only after the third day of fumigation. Therefore, O2*- itself or as precursor of even more toxic oxyradicals appears to be more indicative for ozone-induced leaf damage than H2O2. Ozone also induced significant increases in the activity of antioxidant enzymes (SOD, POX and CAT) after 2 days of fumigation in fungicide untreated plants, while after 4 days of fumigation these enzymes declined to a level lower than in unfumigated plants, due to the oxidative degradation of leaf proteins. This is the first report demonstrating the marked enhancement of plant antioxidative enzymes and the enhanced scavenging of potentially harmful O2*- by fungicides as a mechanism of protecting plants against noxious oxidative stress from the environment. The antioxidant effect of modern fungicides widely used in intense cereal production in many countries represents an important factor when evaluating potential air pollution effects in agriculture.

Acrylates↗
PubMed2001

An approach for estimating the permeability of agricultural films.

Plastic tarps currently used during soil fumigation to control emissions have been shown to be permeable to fumigant vapors, resulting in appreciable losses to the atmosphere. New low-permeability films are being developed to reduce fumigant emissions and increase efficacy. A rapid, reliable, and sensitive method is required to measure the permeability of various films that may be used in new management practices. This manuscript presents an approach for estimating the mass transfer coefficient (h) of fumigant compounds across agricultural films. The h is a measure of the resistance to diffusion which, unlike other measures of permeability, is a property of the film-chemical combination and independent of the concentration gradient across the film. This method uses static sealed cells; fumigant vapor is spiked to one side of the film and the concentrations on both sides of the film are monitored until equilibrium. An analytical model is fitted to the data to obtain h. This model relies on a mass balance approach and includes sorption to and diffusion across the film membrane. The method was tested using two polyethylene films and a very low-permeability film and showed that the method produces a sensitive and reproducible measure of film permeability.

Agriculture↗
PubMed2006

Reducing 1,3-dichloropropene emissions from soil columns amended with thiourea.

Soil fumigants are becoming an important source of volatile organic compounds (VOCs) in air, especially in some agricultural areas. In this study, we used thiourea to construct a reactive surface barrier (RSB) at the soil surface for reducing 1,3-dichloropropene (1,3-D) volatilization. The agrochemical thiourea could rapidly transform volatile 1,3-D to nonvolatile products via an SN2 nucleophilic substitution reaction. A catalytic mechanism in thiourea-amended soil facilitated the conversion process. A packed soil column system was employed to investigate the emissions and distribution of 1,3-D and optimize the original fumigant emission-reduction strategy. Volatilization of 1,3-D from the soil surface was significantly reduced in columns amended with a thiourea RSB compared with that of bare soil. Volatilization flux and cumulative emissions decreased with increasing thiourea application rate and increasing fumigation depth in packed soil columns. Surface amendment with the RSB did not affect the subsurface distribution of 1,3-D in the soil profile. Combined application of a thiourea RSB and plastic tarps had a synergetic effect in emission control and could eliminate the relatively high fumigant flux that occurs upon tarp disruption. Therefore, this reduced-risk practice was very effective in reducing atmospheric emissions of VOCs from soil treatment with halogenated fumigants.

Allyl Compounds↗
PubMed1994

Insecticidal properties of several monoterpenoids to the house fly (Diptera: Muscidae), red flour beetle (Coleoptera: Tenebrionidae), and southern corn rootworm (Coleoptera: Chrysomelidae).

House flies, Musca domestica (L.), and their eggs were treated with 22 monoterpenoids to determine the topical, fumigant, and ovicidal activity of each compound. Fumigant activity of 14 monoterpenoids were examined further using red flour beetles, Tribolium castaneum (Herbst). Third-instar southern corn rootworm, Diabrotica undecimpunctata howardi Barber, were treated with carvacrol, citral, citronellal, menthol, pulegone, verbenol, and verbenone to determine their activity on larvae. Structure-activity relationships were evaluated with the toxicity data. We made comparisons between monocyclic aromatic, acyclic aliphatic, monocyclic aliphatic, and bicyclic aliphatic alcohols, ketones, aldehydes, and acids to determine toxicity differences involving the skeletal structure, amount of saturation, and associated functional groups of monoterapenoids. Ketones were more effective than alcohols in the topical, fumigant (T. castaneum), and ovicidal bioassays and less toxic than an analogous aldehyde in the topical, fumigant (M. domestica), and ovicidal bioassays. Aldehydes were more toxic than alcohols in the topical and fumigant (M. domestica) bioassays. In the topical and ovicidal bioassays, aromatic or acyclic alcohols, or both, were more effective than monocyclic and bicyclic alcohols. Vapors of bicyclic ketones were more toxic than monocyclic ketones to adult M. domestica. Monoterpenoid alcohols containing three carbon-carbon double bonds were more effective than saturated alcohols in the topical and larval bioassays. A mono-unsaturated ketone was more toxic than a structurally similar saturated ketone and two di-unsaturated ketones when it was applied topically to adult M. domestica. A saturated monocyclic ketone inhibited egg hatch more effectively than unsaturated monocyclic ketones.

Acyclic Monoterpenes↗
PubMedDate not supplied

Effect of combined application of methyl isothiocyanate and chloropicrin on their transformation.

Combining several soil fumigants to increase the broad spectrum of pest control is a common fumigation practice in current production agriculture. In this study, we investigated the effect of combined application of chloropicrin and methyl isothiocyanate (MITC) on their transformations and persistence in the environment. In aqueous solution, no direct reaction between MITC and chloropicrin occurred and relatively slow rates of hydrolysis of these compounds were observed in aquatic environments free of suspended solids. The transformation of chloropicrin, however, was accelerated in aqueous solution with MITC because of a reduction reaction with bisulfide (HS(-)), which is a by-product of MITC hydrolysis. In soil, when fumigants were applied simultaneously, the degradation of MITC was suppressed under the bi-fumigant application due to the inhibition of soil microbial activity and a possible abiotic competition with chloropicrin for a limited number of reaction sites on the surface of soil particles. However, the degradation rate of chloropicrin was significantly enhanced in the bi-fumigant soil system, which was primarily attributed to the reaction of chloropicrin and HS(-). Two sequential application approaches were developed to investigate the feasibility of the combined application of metam sodium (parent compound of MITC) and chloropicrin in soil and assess their potential effects on environmental fate. For both application sequences, the degradation of chloropicrin was accelerated and that of MITC, as a major breakdown product of metam sodium, was inhibited in soil.

Chemical Warfare Agents↗
PubMed1995

Toxicology of methyl bromide.

Methyl bromide is widely used as an insecticidal fumigant in food supplies, warehouses, barges, buildings, and furniture. Its popularity as a fumigant is largely attributable to its high toxicity to many pests, the variety of settings in which it can be applied, its ability to penetrate the fumigated substances, and its rapid dissipation following application. Because of its frequent use around humans and human-related activities and its high acute toxicity, methyl bromide-related fatal accidents have occurred. The primary route for human exposure to methyl bromide is inhalation. In California, the most frequent cause of death from methyl bromide exposure in recent years has been unauthorized entry into structures under fumigation. The most frequently reported lesions included pulmonary edema, congestion, and hemorrhage. In recent years, a great deal of effort has been given to the characterization of the toxicity of methyl bromide because of its commercial value and its direct and indirect economic importance. Methyl bromide is acutely very toxic. Subchronically and chronically, the principal target site for methyl bromide appears to be the central nervous system. However, there was no evidence for carcinogenic activity of methyl bromide following the normal environmental exposure routes of inhalation or oral intake through residue on foods. Methyl bromide is clearly genotoxic in vitro and in vivo, as evidenced by the positive results from various tests. The mechanism of toxicity for methyl bromide is currently uncertain, although its alkylating property as well as the possibility of forming a reactive intermediate through metabolic transformation remain attractive hypotheses.

Alkylation↗
PubMed2007

Evaluation of microwave irradiation for analysis of carbonyl sulfide, carbon disulfide, cyanogen, ethyl formate, methyl bromide, sulfuryl fluoride, propylene oxide, and phosphine in hay.

Fumigant residues in hay were "extracted" by microwave irradiation. Hay, in gastight glass flasks, was placed in a domestic microwave oven, and fumigants were released into the headspace by microwave irradiation. Power settings for maximum release of fumigants were determined for carbonyl sulfide (COS), carbon disulfide (CS(2)), cyanogen (C(2)N(2)), ethyl formate (EF), methyl bromide (CH(3)Br), sulfuryl fluoride (SF), propylene oxide (PPO), and phosphine (PH(3)). Recoveries of fortified samples were >91% for COS, CS(2), CH(3)Br, SF, PPO, and PH(3) and >76% for C(2)N(2) and EF. Completeness of extraction was assessed from the amount of fumigant retained by the microwaved hay. This amount was determined from further microwave irradiation and was always small (<5% of the amount obtained from the initial procedure). Limits of quantification were <0.1 mg/kg for COS, CS(2), C(2)N(2), EF, and PH(3) and <0.5 mg/kg for CH(3)Br, SF, and PPO. These low limits were essentially due to the absence of interference from solvents and no necessity to inject large-volume gas samples. The microwave method is rapid and solvent-free. However, care is required in selecting the appropriate power setting. The safety implications of heating sealed flasks in microwave ovens should be noted.

Animal Feed↗