Variations in the emissions of volatile organic compounds from the toner for a specific photocopier.

A laboratory thermal desorption apparatus was used to measure emissions from a number of nominally identical photocopier toners--manufactured to meet the specifications of one specific model copier--when these toners were heated to fuser temperature (180-200 degrees C). The objective was to assess how potential volatile organic compound (VOC) emissions from the toner for a given copier can vary, depending upon the production run and the supplier. Tests were performed on a series of toner (and associated raw polymer feedstock) samples obtained directly from a toner manufacturer, representing two production runs using a nonvented extrusion process, and on toner cartridges purchased from two local retailers, representing three different production lots (histories unknown). The results showed that the retailer toners consistently had up to 350% higher emissions of some major compounds (expressed as microgram of compound emitted/g of toner), and up to 100% lower emissions of others, relative to the manufacturer toners (p < or = 0.01). The manufacturer toners from one production run had emissions of certain compounds, and of total VOCs, that were modestly higher (13-18%) than those from the other run (p < or = 0.01). The emission differences between the retailer and manufacturer toners are probably due to differences in the manufacturing processes and/or feedstocks used to produce the toners from these different sources.

Dissociation of sulfur hexafluoride tracer gas in the presence of an indoor combustion source.

As an odorless, nontoxic, and inert compound, sulfur hexafluoride (SF6) is one of the most widely used tracer gases in indoor air quality studies in both controlled and uncontrolled environments. This compound may be subject to reactions with water vapor under elevated temperature to form acidic inorganic compounds such as HF and H2SO4. Thus, in the presence of unvented combustion sources such as kerosene heaters, natural gas heaters, gas log fireplaces, candles, and lamps, the SF6 dissociation may interfere with measurements of the emissions from these sources. Tests were conducted in a research house with a vent-free natural gas heater to investigate these potential interferences. It was observed that the heater operation caused about a 5% reduction of SF6 concentration, which can be an error source for the ventilation rate measurement and consequently the estimated pollutant emission rates. Further analysis indicates that this error can be much greater than the observed 5% under certain test conditions because it is a function of the ventilation flow rate. Reducing the tracer gas concentration has no effect on this error. A simple theoretical model is proposed to estimate the magnitude of this error. The second type of interference comes from the primary and secondary products of the SF6 dissociation, mainly H2SO4, SO2, HF, and fine particulate matter (PM). In the presence of approximately 5 ppm SF6, the total airborne concentrations of these species increased by a factor of 4-10. The tests were performed at relatively high SF6 concentrations, which is necessary to determine the interferences quantitatively. The second type of interference can be significantly reduced if the SF6 concentration is kept at a low ppb level.

Development and testing of a whole-air sampler for measurement of personal exposure to volatile organic compounds.

A small and relatively lightweight (3.35 kg) whole-air (canister) sampler that can be worn to monitor personal exposures to volatile organic compounds was developed and evaluated. The prototype personal whole-air sampler (PWAS) consists of a 1-l canister, a mass flow controller, two 1.3 amp hour batteries, a DC/DC converter, and an electronics module with a digital display for the sampling set point, actual flow rate, and battery voltage. The sampler (25.5 x 22.5 x 7.5 cm) fits into a laptop computer carrying case and is able to collect a 900 ml sample at a linear flow rate over 12-16 hours. Laboratory tests demonstrated that the sample flow rate was not affected by temperature or the activity of the person wearing the sampler. Recoveries of methylene chloride, chloroform, 1,1,1-trichloroethane, benzene, n-octane, o-xylene, n-decane, and p-dichlorobenzene averaged 89% or better for three final prototype samplers. Recoveries were slightly lower for vinyl chloride (74%) and n-dodecane (82%). The precision for the three prototypes was excellent during laboratory tests with the coefficient of variation (CV) < 10% for all the test compounds. Although the unit was designed for use as a personal whole-air sampling system, it can also be used as an extremely compact microenvironmental whole-air sampler.

Evaluation of methods for monitoring the potential exposure of small children to pesticides in the residential environment.

A nine-home pilot study was conducted to evaluate monitoring methods in the field that may be used to assess the potential exposures of children aged 6 months to 5 years to pesticides found in the home environment. Several methods, some of which were newly developed in this study, were tested for measuring pesticide residues in indoor air, carpet dust, outdoor soil, and on the children's hands. Information was also collected on household characteristics, pesticides used and stored at the residence, and children's activities. Pesticides were detected at all nine study homes. With the exception of one home, at least one pesticide was detected in all matrices sampled at each house. Of the 30 target pesticides, 23 were detected during the study. The most frequently detected pesticides were chlordane, chlorpyrifos, dieldrin, hepatachlor, and pentachlorophenol. The greatest number of pesticides and highest concentrations were found in carpet dust. The results of these investigations will be discussed in terms of performance of the methods and the distribution of pesticides across the various media sampled.