William R. Burg

Measurements of airborne aflatoxins during the handling of contaminated corn

Sample of airborne dust generated the handling of aflatoxin-contaminated corn were collected and analyzed to assess potential exposures of farmers and other agricultural workers to these mycotoxins. Using high volume total dust samplers and a high volume Andersen sampler, downwind dust samples were collected on glass filter when contaminated corn was transferred by augers from a storage bin into a wagon and back into the storage bin. The aflatoxin B1 content of the 15 dust samples ranged from 12.5 to 204.3 ppb, with an average of 138 ppb; the aflatoxin B2 content ranged from 1.1 to 41.6 ppb, with an average of 24.6 ppb. The B1 and B2 levels of contamination in the bulk corn were 223.9 and 17.5 ppb, respectively. The gravimetric dust concentration in the air ranged from 7 mg/m3 to 417 mg/m3. The samples taken with an Andersen sampler indicate the dust is relatively coarse with only approximately 17% less than 7 micrometer. An analysis of the dust from each stage showed higher levels of aflatoxins in the larger first-stage particles than in the finer particles on the succeeding stages. The results of this study indicate that the dust generated when handling contaminated commodities also may be contaminated and represent a potential inhalation hazard. This fact, coupled with the extreme toxicity and carcinogenicity previously demonstrated in animal studies, suggests that appropriate measures be taken to prevent worker exposure during handling of contaminated materials.

Occupational aspects of passive smoking

Peak carbon monoxide levels of 30 ppm were found during a work shift in a poorly ventilated tavern. A time-weighted average concentration of 17 ppm CO was found as well as elevated particulate levels. The occupational exposure to cigarette effluents is discussed in light of OSHA regulations.

Determination of airborne 2,4-toluenediisocyanate vapors.

An accurate and convenient sampling and analytical method was developed for airborne 2,4-toluenediisocyanate (TDI). A chromophoric derivatizing reagent was used to convert the TDI to a stable urea derivative during collection for subsequent quantification by liquid chromatography. The overall accuracy (at the 95% confidence level) and precision of the method are +/- 7.9% and +/- 10.0% respectively under laboratory conditions. Long term stability was observed for both the reagent coated sorbent tube and the TDI urea derivative. A TDI concentration of 1 ppb can be detected by taking a 15-1 sample volume.

The generation of low concentrations of 2,4-toluenediisocyanate (TDI)

A convenient and accurate method for generating low concentrations of 2,4-Toluenediisocyanate (TDI) was developed using tetrafluoroethylene Teflon (TFE) permeation tubes. The permeation tubes were prepared by sealing approximately 1.5 grams of practical grade TDI in clean spaghetti tubing with solid TFE rod held in place with crimped aluminum Swagelok ferrules. Tubes of 4.762 mm ID and 0.762 mm wall thickness and 6.477 mm ID and 0.254 mm wall thickness were sealed with 5.08 mm and 6.350 mm TFE rods, respectively. Standard ferrules (0.25 inch) were drilled out slightly to accommodate the larger tubing. Using a commercially available air bath capable of maintaining a temperature within 0.05° K, the permeation tubes were kept at 303° K, 323° K and 343° K. The TDI was swept from the thermostated chamber with dry nitrogen and further diluted with clean dry air to the desired concentrations. The permeation rate was constant when the tubes were maintained at a constant temperature, however when the tube experien...

Solid absorbent method for sampling and analysis of nitrogen dioxide in ambient air

A sampling and analysis system was developed for measuring concentrations of nitrogen dioxide in ambient air. Copper shot was found to be an effective absorbent for collecting samples at ambient levels. The analytical system was based on the desorption of the sample from the copper by heating in a hydrogen carrier stream. The desorbed sample was then determined by a combination of catalytic pyrolysis, which converted it to ammonia, and a Coulson Conductivity Detector. Data are presented showing overall recovery, effects of storage of collected samples, results for 24-hour sampling and interferences. Studies indicated the feasibility of the method for short time sampling as well as for 24-hour sampling periods. The detection limit was shown to be as little as 100 ng NO2 in laboratory studies. This solid absorbent method provides a simple, convenient, and compact means for air sampling.

The development of an air sampling and analytic method for o-phenylenediamine in an industrial environment

A new method for monitoring o-phenylenediamine (OPD) in the industrial environment was developed. Some aromatic amines such as OPD are difficult to collect and analyze directly because they are sensitive to oxidation. The method developed overcomes this difficulty by derivatizing the OPD directly upon collection. The OPD vapor is drawn through a bubbler containing acetic anhydride to form the relatively stable 1,2-diacetamidobenzene. The acetic anhydride solution is analyzed by means of high performance liquid chromatography (HPLC), and the diacetamido derivative quantified. The analysis is linear for standard solutions in the range of 0.5 microgram/mL to over 0.5 mg/mL. Air concentrations of OPD were prepared by passing a metered stream of nitrogen through a class tube packed with OPD crystals and diluting the stream with a metered air stream to achieve the desired level. The collection efficiency and conversion of OPD to the derivative was found to approach 100% at vapor concentrations of 0.09 mg/m3 but was reduced to about 60% at 0.02 mg/m3. The poor recovery at low concentrations appeared to be at least in part due to wall adsorption. Moisture had little effect on sample collection and analysis. O-Toluenediamine, chemically similar to OPD, was found to interfere in the analysis.

A solid sorbent air sampling method for O-phenylenediamine (OPD)

A method for collecting, storing and quantifying airborne vapors of O-phenylenediamine (OPD) in the workplace has been developed. The vapors are collected on 100 mg of Tenax-GC packed in 4 mm ID glass tubing wrapped with aluminum foil. The OPD is desorbed and derivatized using a 10% solution of acetic anhydride in acetonitrile to form diacetamidobenzene (DAAB). The DAAB was subsequently quantified by injecting 10 µL of the solution into a liquid chromatograph equipped with a UV-detector (254 nm), a Partisil PXS PAC column and a 7% methanol in 1-chlorobutane mobile phase. The limit of detection is approximately 10 ng. Samples collected from test atmospheres containing OPD in dry air at concentrations ranging from 0.05 to 0.2 mg/m3 gave an overall recovery of 86.6%. Recoveries of samples collected from atmospheres humidified to 80% relative humidity were 79%. The capacity of the tube is at least 25 µg which is sufficient for either short or long term samples.