Particulate matter (PM) exposure and health effects have become top US environmental research agenda items over the last decade. Environmental epidemiological studies rely on information from both sides of the dose-response equation: risk factor measures and health outcome data The ability to resolve relationships from environmental data depends upon the quantity, accuracy, specificity and precision of both. Although health surveillance and data collection methods have improved dramatically through database system advances, the techniques for PM exposure are not adequate.
At least three major limitations currently exist for PM measurement. First, PM exposure monitoring is too expensive. Total costs must be reduced by 1–2 orders of magnitude for monitoring within populations to be affordable. Currently, high capital costs make purchasing hundreds of samplers for a single study impractical. Overcoming this obstacle would be extremely beneficial to several types of studies, including measurements of community exposure, exposure variability between individuals in heterogeneous populations, and the relationships among indoor, outdoor, and total personal exposure levels.
Second, PM exposure assessment technology is limited by size, weight, noise, and power constraints. This applies to both area samplers (stationary monitors placed in commonly occupied spaces) and personal samplers (monitors worn by subjects at the breathing zone). The operating noise of area samplers can be very undesirable to study participants. Personal samplers are typically smaller than stationary samplers, but their pumps are usually loud, heavy and bulky. These inconveniences alter subjects' behavior and produce non-representative exposure estimates. Also, the most susceptible populations, children, the elderly, and those with respiratory ailments, often have limited tolerance for such samplers.
Third, simultaneous measurements of several PM characteristics by a single PM device are not typically available. As a result, several types of samplers must be used simultaneously to obtain PM mass, particle size distributions, chemical composition and optical properties. A single ‘multi-parameter’ sampler that could obtain this range of measurements would be much more practical, especially to identify the sources and mechanisms of health effects.
There is known in the art techniques for measuring PM using resonators, see U.S. Pat. No. 3,561,253. Also, U.S. Pat. No. 5,892,141 uses electrostatic precipitation onto an oscillating surface. U.S. Pat. No. 6,510,727 uses piezoelectric resonators which are provided with at least one collection surface for the particles to be analyzed. Thermoelectric particle precipitators are known in the art, see U.S. Pat. No. 6,666,905. Thermophoretic pumps and concentrators are known in the art, see U.S. Pat. No. 6,413,781 All the aforementioned patents are hereby incorporated herein by reference in their entirety.
A significant benefit of the miniaturized PM samplers in accordance with the present invention is the ability to use them in mail-out surveys where they are deployed in-home, or on-person, by survey participants, reducing the need for trained field personnel. A number of suitable simple miniaturized exposure monitoring devices have been developed for toxic gaseous pollutants, including carbon monoxide, oxides of nitrogen, formaldehyde, volatile organic compounds, and radon.
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