as the cause of numerous recent outbreaks of diarrheal disease in humans. C. parvum oocysts are known to be vulnerable to high temperature for long exposure times. I. A. Harp and colleagues investigated the effect of pasteurization temperatures for short duration on oocyst infectivity in water and milk. Results indicate that high-temperature, shorttime pasteurization conditions (71.7 °C for 15 s) are sufficient to destroy the infectivity of the oocysts. This treatment could be of special benefit to people with weakened immune systems, who are more vulnerable to waterborne infections. (Appl. Environ. Microbiol. 1996, 62, 2866-68)
GREEN CHEMISTRY Cellulose esters Cellulose esters have attracted attention as potential biodegradable polymers. Often overlooked is the fact that cellulose esters are copolymers, with the monomer composition or distribution determining biodegradability of these cellulose derivatives. C. M. Buchanan and co-workers used laboratory-scale simulations of municipal composting to determine how the degree of substitution influences the miscibility and biodegradability of cellulose acetate polymer blends. The authors worked with cellulose acetates of degrees of substitution of 2.06 (CA2.0) and 2.49 (CA2.5) in blends with and without added plasticizer (poly(ethylene glycol)). They report that the CA2.0 and CA2.5 can be blended to form miscible blends with useful physical properties. (/. Environ. Polym. Degrad. 1996, 4, 179-95)
Membranes vs. mussels Several factors limit the usefulness of bivalve mollusks and other living organisms used as environmental sentinels to measure contaminants. Consequently, researchers are evaluating nonliving contaminant accumulators. C. S. Hofelt and D. Shea compared semipermeable membrane devices (SPMDs) made from low-density polyethylene tubing containing 95% triolein and caged blue mussels at five sites in New Bedford Harbor, Mass. A significant correlation (p < 0.01) was found between pesticide concentrations in the membrane and in the mussels. However, accumulation by the mussels was two-fold higher than by the SPMD. SPMD uptake rate and equilibrium could be altered by varying the membrane thickness, surface area, and lipid substrate volume. Such data are important for optimizing design of SPMDs for specific applications. {Environ. Sci. Technol., this issue, pp. 154-59)
pylene is effective in enhancing the mechanical properties of fiber-reinforced polypropylene. (J. Appl. Polym. Sci. 1996, 61, 1423-30)
GROUNDWATER Wetlands nitrate Much uncertainty exists over the mechanisms by which wetlands function as a sink for nitrate. Wetlands may reduce nitrate by plant uptake and denitrification; however, nitrate loss may also result from dilution effects caused by upwelling groundwater or infiltration of rainwater. J. L. Starr and colleagues used a forced-gradient cluster well technique to simulate the intermittent saturated conditions that occur during groundwater recharge periods in these soil systems. The researchers used bromine as a tracer, with and without the addition of dextrose, and mapped lateral flow paths. Rates of nitrogen loss were substantially higher with added dextrose, indicating that the nitrate was denitrified or mobilized into microbial biomass. (/. Environ. Qual. 1996, 25, 917-23)
Wood fiber reinforcement Wood fiber is attracting interest as a reinforcement material in thermoplastic and thermosetting polymers. Wood fiber is light, renewable, and biodegradable, and it enhances mechanical properties of plastics. J. R. Collier and co-workers used sweet gum wood fiber to study simultaneous and sequential compounding of polypropylene. They report that malleation of the polypropylene with maleic anhydride enhances the mechanical properties of wood fiber to improve compatibilization. They conclude that malleation of polypro-
HEALTH Acid aerosols and health Much of the concern about acid precipitation has focused on its ecological effects and indirect health effects in mobilizing toxic metals. But new concerns have emerged about the potential direct human health effects of inhaling acid aerosols. D. W Dockery and colleagues used a questionnaire to collect respiratory health data from parents and guardians of more than 13,000 children
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from 24 nonurban communities in the United States and Canada. Air quality and meteorological data were collected for each community. Children living in the areas with the highest levels of aerosol acidity were more likely to report at least one episode of bronchitis compared with children in the least polluted communities. No other respiratory symptoms (wheeze, asthma, cough, phlegm) were significantly higher in the communities with higher aerosol acidity levels. (.Environ. Health Perspect. 1996, 104, 500-5)
Ozone and asthma Previous studies of ozone pollution's effects in triggering asthma have relied only on outdoor ozone measurements from stationary site monitors to gauge individual exposure. These studies ignore the effects of airborne allergen exposure, which can interact with ozone to produce symptoms. R. J. Delfino and coworkers studied outdoor and personal ozone exposure in 12 young asthma patients while concurrently measuring concentrations of fine particles, fungal spores, and pollen. Asthma symptoms and medication use increased with unexpectedly low levels of personal ozone exposure. Numbers of fungal spores also were associated with increased asthmatic symptoms and medication use, whereas pollen and fine particles were not. The authors report that outdoor ozone readings may understate ozone's effects on asthma patients. [Am. J. Respir. Crit. Care Med. 1996, 154, 633-41)
Waste site exposure Environmental policy makers often assume that living near hazardous waste sites may be associated with increased intake of toxic chemicals
