Evaluation of CS (o-chlorobenzylidene malononitrile) concentrations during U.S. Army mask confidence training.

All soldiers in the U.S. Army are required to complete mask confidence training with o-chlorobenzylidene malononitrile (CS). To instill confidence in the protective capability of the military protective mask, CS is thermally dispersed in a room where soldiers wearing military protective masks are required to conduct various physical exercises, break the seal of their mask, speak, and remove their mask. Soldiers immediately feel the irritating effects of CS when the seal of the mask is broken, which reinforces the mask's ability to shield the soldier from airborne chemical hazards. In the study described in this article, the authors examined the CS concentration inside a mask confidence chamber operated in accordance with U.S. Army training guidelines. The daily average CS concentrations ranged from 2.33-3.29 mg/m3 and exceeded the threshold limit value ceiling, the recommended exposure limit ceiling, and the concentration deemed immediately dangerous to life and health. The minimum and maximum CS concentration used during mask confidence training should be evaluated.

Using gas chromatography with ion mobility spectrometry to resolve explosive compounds in the presence of interferents.

Ion mobility spectrometry (IMS) is a valued field detection technology because of its speed and high sensitivity, but IMS cannot easily resolve analytes of interest within mixtures. Coupling gas chromatography (GC) to IMS adds a separation capability to resolve complex matrices. A GC-IONSCAN® operated in IMS and GC/ IMS modes was evaluated with combinations of five explosives and four interferents. In 100 explosive/interferent combinations, IMS yielded 21 false positives while GC/ IMS substantially reduced the occurrence of false positives to one. In addition, the results indicate that through redesign or modification of the preconcentrator there would be significant advantages to using GC/ IMS, such as enhancement of the linear dynamic range (LDR) in some situations. By balancing sensitivity with LDR, GC/ IMS could prove to be a very advantageous tool when addressing real world complex mixture situations.

Identification of compounds formed during low temperature thermal dispersion of encapsulated o-chlorobenzylidene malononitrile (CS riot control agent).

U.S. Army chemical mask confidence training is conducted in an enclosed chamber where airborne o-chlorobenzylidene malononitrile (also known as CS or "tear gas") is generated using a low temperature (150-300 degrees C) dispersal method. CS capsules are placed onto a flame-heated aerosol generator that melts the capsules and disperses CS into the chamber. To instill confidence in chemical protective equipment, trainees are required to break the seal of their chemical protective mask, resulting in the immediate irritation of their eyes, nose, throat, and lungs. Solid phase micro extraction (SPME) sample collection techniques were used inside the chamber, followed by gas chromatography and mass spectrometry (GC/MS) to identify unintended thermal degradation products created during the CS dispersal process. The temperature of the aerosol generator averaged 257 degrees C, and 17 thermal degradation products were identified. To characterize the relationship between temperature and the types of CS thermal degradation products formed, CS was dispersed in a tube furnace at controlled temperatures from 150-300 degrees C and analyzed using the same method. There was a graded response between temperature and the number of thermal degradation products formed, with one product formed at 150 degrees C and 15 products formed at 300 degrees C. Two additional products were identified in the chamber experiment when compared with the tube furnace experiment. These products are likely the result of molten CS dripping directly into the aerosol generator's flame, which averaged 652 degrees C. To prevent undesirable degradation products during thermal dispersion of CS, a delivery system designed to contain the molten CS and maintain a consistent temperature near 150 degrees C is recommended.

Chemical agent identification by field-based attenuated total reflectance infrared detection and solid-phase microextraction.

Attenuated total reflectance Fourier transform infrared (ATR-FT-IR) spectroscopy is used to identify liquid and solid-phase chemicals. This research examines the feasibility of identifying vapor-phase chemicals using a field-portable ATR-FT-IR spectrometer (TravelIR) combined with solid-phase microextraction (SPME). Two nerve agent simulants, diisopropyl methylphosphonate (DIMP) and di-methyl methylphosphonate (DMMP), and three sorbent polymers were evaluated. Each polymer was deposited as a thin film on the instrument's sampling interface to partition and concentrate the simulants from air samples prepared in Tedlar bags. The lowest vapor concentrations identified were 50 ppb (v/v) (DIMP) and 250 ppb (v/v) (DMMP). The ATR-FT-IR instrument demonstrated a linear response at concentrations of 1 ppm (v/v) and below. Increasing the sample exposure time, the sample air velocity, and the film thickness was demonstrated to increase the amount of analyte extracted from the air sample. This research demonstrates that it is feasible to use a portable ATR-FT-IR spectrometer with SPME sampling to detect and identify vapor-phase chemicals.

Chromate content versus particle size for aircraft paints.

Many industries rely on the corrosion inhibiting properties of chromate-containing primer paints to protect metal from oxidation. However, chromate contains hexavalent chromium (Cr(6+)), a known human carcinogen. The concentration of Cr(6+) as a function of paint particle size has important implications to worker health and environmental release from paint facilities. This research examines Cr(6+) content as a function of particle size for three types of aircraft primer paints: solvent-based epoxy-polyamide, water-based epoxy-polyamide, and solvent-based polyurethane. Cascade impactors were used to collect and separate paint particles based on their aerodynamic diameter, from 0.7 to 34.1 microm. The mass of the dry paint collected at each stage was determined and an atomic absorption spectrometer was used to analyze for Cr(6+) content. For all three paints, particles less than 7.0 microm contained disproportionately less Cr(6+) per mass of dry paint than larger particles, and the Cr(6+)concentration decreased substantially as particle size decreased. The smallest particles, 0.7 to 1.0 microm, contained approximately 10% of the Cr(6+) content, per mass of dry paint, compared to particles larger than 7.0 microm. The paint gun settings of air to paint ratio was found to have no influence on the Cr(6+) bias.

Chromate dissociation from three types of paint particles.

Chromate-containing primer paints are used to inhibit corrosion on metal surfaces. Though chromate contains hexavalent chromium (Cr(6+)), a human carcinogen, there is little epidemiological evidence of increased lung cancer among spray painters. One reason may be that the paint matrix hinders the release of Cr(6+) from the paint particle during the time that the particle is within the lungs. This study measures the mass of Cr(6+) released from particles originating from three types of paint particles: solvent-borne epoxy, water-borne epoxy, and polyurethane. Impingers were used to collect paint particles into water and particles were held in the water at rest for 1 and 24 h residence times. Particles were then separated from the water by centrifugation. The supernatant was tested for dissolved Cr(6+), which was compared to the total Cr(6+) (dissolved Cr(6+) plus Cr(6+) in particles). The mean fractions of Cr(6+) released into the water after 1 and 24 hours for each primer averaged: 70 and 85 (solvent epoxy), 74 and 84% (water epoxy), and 94 and 95% (polyurethane). Correlations between particle size and the fraction of Cr(6+) released indicate that smaller particles (<5 microm) release a larger fraction of Cr(6+) versus larger particles (>5 microm).