David L. MacIntosh

Distal femoral varus osteotomy for valgus deformity of the knee.

Twenty-four patients who had degenerative arthritis of the lateral compartment of the knee that was associated with a valgus deformity and a superolateral tilt of the joint line were treated by distal femoral varus osteotomy. A surgical technique that was designed to produce a horizontal joint line and a tibiofemoral angle of zero degrees is described. At an average length of follow-up of four years, twenty-two of twenty-four patients had a successful result as judged by our protocol for evaluation. One osteotomy had to be revised for failure of fixation, and one patient had a pulmonary embolism that had a satisfactory outcome after the administration of anticoagulants. One patient required manipulation of the knee at six months. The simple surgical technique that we used was effective in realigning the femoral with the tibial axis in patients who had a valgus deformity of the knee, a superolateral tilt of the joint line, and osteoarthritis of the lateral compartment.

Demographic Covariates of Residential Recycling Efficiency

To obtain information on recycling behavior for selected populations, demographic data and measurements of materials in trash containers and recycling bins were collected from a random sample of 87 residences in Athens-Clarke County, Georgia. The recycling efficiency (RE) for each household had a mean of 45% and exhibited a bimodal distribution characterized by 1 group of households with near-zero RE and a second group with RE from 75% to 100%. Annual household income, home-ownership status, and level of education attained by the lead recycler were significantly associated with RE. The results of this study indicate that greater participation in recycling programs among low socioeconomic status households in this population may yield greater increases in waste reduction than enhanced RE of current participants. Additional research is required to evaluate the degree to which these findings can be generalized to other communities.

A longitudinal investigation of selected pesticide metabolites in urine

As part of a longitudinal investigation of environmental exposures to selected chemical contaminants, concentrations of the pesticide metabolites 1-naphthol (1NAP), 3,5,6-trichloro-2-pyridinol (TCPY), malathion dicarboxylic acid (MDA), and atrazine mercapturate (AM) were measured in repeated samples obtained from 80 individuals in Maryland during 1995–1996. Up to six urine samples were collected from each individual at intervals of approximately 8 weeks over a 1-year period (i.e., one sample per participant in each of six cycles). 1NAP (median=4.2 µg/l and 3.3 µg/g creatinine) and TCPY (median=5.3 µg/l and 4.6. µg/g creatinine) were present in over 80% of the samples, while MDA and AM were detected infrequently (6.6% and <1% of samples, respectively). Geometric mean (GM) concentrations of 1NAP in urine did not vary significantly among sampling cycles. In contrast, GM concentrations of TCPY were significantly greater in samples collected during the spring and summer of 1996 than in the preceding fall and winter. Repeated measurements of 1NAP and TCPY from the same individual over time were highly variable. The average range of 1NAP and TCPY concentrations from the same individual were approximately 200% and 50% greater than the respective population mean levels. Geometric mean (GM) TCPY concentrations differed significantly between Caucasian (n=42, GM=5.7 µg/g creatinine) and African-American (n=11, GM=4.0 µg/g) participants and among education levels, but were not significantly different among groups classified by gender, age, or household income. In future research, environmental measurements of the parent compounds and questionnaire data collected concurrently with the biomarker data will be used to characterize the determinants of variability in the urinary pesticide metabolite levels.

Dietary exposure to chlorpyrifos and levels of 3,5,6-trichloro-2-pyridinol in urine

Information on associations between chlorpyrifos residues in food and personal exposure to chlorpyrifos would be valuable for evaluating the relationship between personal exposure and possible health effects. We used food consumption records, chlorpyrifos levels in duplicate plates, and measures of 3,5,6-trichloro-2-pyridinol (TCPy) in urine obtained from human volunteers in the National Human Exposure Assessment Survey in Maryland (NHEXAS-MD) to evaluate a food consumption–chemical residue model for estimating dietary intake of chlorpyrifos. Model inputs were the NHEXAS-MD food consumption records and chlorpyrifos residues in specific foods measured in the U.S. Food and Drug Administration Total Diet Study (TDS) market baskets from 1993 to 1997. The estimated mean and standard deviation of chlorpyrifos concentration (μg/kg) in duplicate plates (n=203) were within 20% and 50%, respectively, of the corresponding parameters of measured chlorpyrifos levels. However, predicted and measured concentrations in the 78 duplicate plates with detectable levels of chlorpyrifos were not significantly associated according to Spearman correlation analysis (r=0.04, p=0.7667) and linear regression (p=0.2726). Measured and estimated chlorpyrifos intakes for observations with non-zero values for each intake measure (n=71) were moderately associated on a rank (Spearmans r=0.24, p=0.0462) and linear basis (regression r2=0.07, p=0.0242). Measured intakes of chlorpyrifos from food and urinary TCPy were significantly correlated in rank order (n=87, Spearmans r=0.30, p=0.0041) and linear (n=87, Pearsons r=0.22, p=0.0409) analyses. Correlation coefficients between estimated intake of chlorpyrifos from food and TCPy were significantly different from zero (n=87; Spearmans r=0.22, p=0.0393; Pearsons r=0.21, p=0.0479). Comparing mean measured chlorpyrifos intake from food (0.46 μg/day) to mean estimated TCPy excretion via urine (6.3 μg/day), dietary intake of chlorpyrifos accounted for approximately 7% of TCPy in this population. These findings suggest the food consumption–chemical residue model can yield reasonably accurate estimates of the population distribution of dietary chlorpyrifos intake, but has little ability to predict dietary exposure for individuals; and that intake of chlorpyrifos from food is a minor contributor to TCPy in urine.

The benefits of whole-house in-duct air cleaning in reducing exposures to fine particulate matter of outdoor origin: a modeling analysis.

Health risks of fine particle air pollution (PM2.5) are an important public health concern that has the potential to be mitigated in part by interventions such as air cleaning devices that reduce personal exposure to ambient PM2.5. To characterize exposure to ambient PM2.5 indoors as a function of residential air cleaners, a multi-zone indoor air quality model was used to integrate spatially resolved data on housing, meteorology, and ambient PM2.5, with performance testing of residential air cleaners to estimate short-term and annual average PM2.5 of outdoor origin inside residences of three metropolitan areas. The associated public health impacts of reduced ambient PM2.5 exposure were estimated using a standard health impact assessment methodology. Estimated indoor levels of ambient PM2.5 varied substantially among ventilation and air cleaning configurations. The median 24-h average indoor–outdoor ratio of ambient PM2.5 was 0.57 for homes with natural ventilation, 0.35 for homes with central air conditioning (AC) with conventional filtration, and 0.1 for homes with central AC with high efficiency in-duct air cleaner. Median modeled 24-h average indoor concentrations of PM2.5 of outdoor origin for those three configurations were 8.4, 5.3, and 1.5 μg/m3, respectively. The potential public health benefits of reduced exposure to ambient PM2.5 afforded by air cleaning systems were substantial. If the entire population of single-family homes with central AC in the modeling domain converted from conventional filtration to high-efficiency in-duct air cleaning, the change in ambient PM2.5 exposure is estimated to result in an annual reduction of 700 premature deaths, 940 hospital and emergency room visits, and 130,000 asthma attacks in these metropolitan areas. In addition to controlling emissions from sources, high-efficiency whole-house air cleaner are expected to reduce exposure to particles of outdoor origin and are projected to be an effective means of managing public health impacts of ambient particle pollution.

Control of asthma triggers in indoor air with air cleaners: a modeling analysis

BackgroundReducing exposure to environmental agents indoors shown to increase asthma symptoms or lead to asthma exacerbations is an important component of a strategy to manage asthma for individuals. Numerous investigations have demonstrated that portable air cleaning devices can reduce concentrations of asthma triggers in indoor air; however, their benefits for breathing problems have not always been reproducible. The potential exposure benefits of whole house high efficiency in-duct air cleaners for sensitive subpopulations have yet to be evaluated.MethodsWe used an indoor air quality modeling system (CONTAM) developed by NIST to examine peak and time-integrated concentrations of common asthma triggers present in indoor air over a year as a function of natural ventilation, portable air cleaners, and forced air ventilation equipped with conventional and high efficiency filtration systems. Emission rates for asthma triggers were based on experimental studies published in the scientific literature.ResultsForced air systems with high efficiency filtration were found to provide the best control of asthma triggers: 30–55% lower cat allergen levels, 90–99% lower risk of respiratory infection through the inhalation route of exposure, 90–98% lower environmental tobacco smoke (ETS) levels, and 50–75% lower fungal spore levels than the other ventilation/filtration systems considered. These results indicate that the use of high efficiency in-duct air cleaners provide an effective means of controlling allergen levels not only in a single room, like a portable air cleaner, but the whole house.ConclusionThese findings are useful for evaluating potential benefits of high efficiency in-duct filtration systems for controlling exposure to asthma triggers indoors and for the design of trials of environmental interventions intended to evaluate their utility in practice.

Temporal variability of microenvironmental time budgets in Maryland

Information on human time-activity patterns is often required to interpret environmental exposure data fully and to implement exposure assessment models. Data on short-term time-activity patterns for individuals, such as 1-day measurements, are relatively abundant. The reliability of such data for use in chronic exposure (e.g., 1 or more years) assessments performed for evaluation of health risks is not well understood. As part of the NHEXAS-Maryland investigation, daily time budget data for seven microenvironments were collected from 80 people during as many as six 1-week Cycles over a 12-month period. The data were summarized and analyzed statistically by sampling Cycle, day of week, and individual to characterize long-term average microenvironmental time budgets and to identify their determinants. Median times spent in transit, indoors at home, outside at home, indoors at work or school, outdoors at work or school, indoors at other locations, and outdoors at other locations were found to vary significantly, although not substantively in many cases, by time of year (i.e., Cycle), by day of week, and by individuals. Time budgets for most of the microenvironments also exhibited significant variability by gender, age group, education level, annual household income, and work status. The results indicate that short-term (e.g., 1-day) measures of microenvironmental time budgets for individuals are unlikely to be representative of their long-term patterns. Thus, health risk or epidemiological assessments performed for a population mean or specific quantile may be relatively insensitive to when time budget data were collected. However, the accuracy of such assessments performed for individuals is likely to be greatly improved by collection of time budget data from numerous points in time.

Whole House Particle Removal and Clean Air Delivery Rates for In-Duct and Portable Ventilation Systems

Abstract A novel method for determining whole house particle removal and clean air delivery rates attributable to central and portable ventilation/air cleaning systems is described. The method is used to characterize total and air-cleaner-specific particle removal rates during operation of four in-duct air cleaners and two portable air-cleaning devices in a fully instrumented test home. Operation of in-duct and portable air cleaners typically increased particle removal rates over the baseline rates determined in the absence of operating a central fan or an indoor air cleaner. Removal rates of 0.3- to 0.5-μm particles ranged from 1.5 hr−1 during operation of an in-duct, 5-in. pleated media filter to 7.2 hr−1 for an in-duct electrostatic air cleaner in comparison to a baseline rate of 0 hr−1 when the air handler was operating without a filter. Removal rates for total particulate matter less than 2.5 μm in aerodynamic diameter (PM2.5) mass concentrations were 0.5 hr−1 under baseline conditions, 0.5 hr−1 during operation of three portable ionic air cleaners, 1 hr−1 for an in-duct 1-in. media filter, 2.4 hr−1 for a single high-efficiency particle arrestance (HEPA) portable air cleaner, 4.6 hr−1 for an in-duct 5-in. media filter, 4.7 hr−1 during operation of five portable HEPA filters, 6.1 hr−1 for a conventional in-duct electronic air cleaner, and 7.5 hr−1 for a high efficiency in-duct electrostatic air cleaner. Corresponding whole house clean air delivery rates for PM2.5 attributable to the air cleaner independent of losses within the central ventilation system ranged from 2 m3/min for the conventional media filter to 32 m3/min for the high efficiency in-duct electrostatic device. Except for the portable ionic air cleaner, the devices considered here increased particle removal indoors over baseline deposition rates.

A Comparison of Four Gravimetric Fine Particle Sampling Methods

ABSTRACT A study was conducted to compare four gravimetric methods of measuring fine particle (PM2.5) concentrations in air: the BGI, Inc. PQ200 Federal Reference Method PM2.5 (FRM) sampler; the Harvard-Marple Impactor (HI); the BGI, Inc. GK2.05 KTL Respirable/Thoracic Cyclone (KTL); and the AirMetrics MiniVol (MiniVol). Pairs of FRM, HI, and KTL samplers and one MiniVol sampler were collocated and 24-hr integrated PM2.5 samples were collected on 21 days from January 6 through April 9, 2000. The mean and standard deviation of PM2.5 levels from the FRM samplers were 13.6 and 6.8 μg/m3, respectively. Significant systematic bias was found between mean concentrations from the FRM and the MiniVol (1.14 μg/m3, p = 0.0007), the HI and the MiniVol (0.85 μg/m3, p = 0.0048), and the KTL and the MiniVol (1.23 μg/m3, p = 0.0078) according to paired t test analyses. Linear regression on all pairwise combinations of the sampler types was used to evaluate measurements made by the samplers. None of the regression intercepts was significantly different from 0, and only two of the regression slopes were significantly different from 1, that for the FRM and the MiniVol [β1 = 0.91, 95% CI (0.83–0.99)] and that for the KTL and the MiniVol [ = 0.88, 95% CI (0.78–0.98)]. Regression R2 terms were 0.96 or greater between all pairs of samplers, and regression root mean square error terms (RMSE) were 1.65 μg/m3 or less. These results suggest that the MiniVol will underestimate measurements made by the FRM, the HI, and the KTL by an amount proportional to PM2.5 concentration. Nonetheless, these results indicate that all of the sampler types are comparable if ~10% variation on the mean levels and on individual measurement levels is considered acceptable and the actual concentration is within the range of this study (5–35 μg/m3).

Prevalence and implementation of IAQ programs in U.S. schools.

In this study, we determined the extent to which U.S. schools are implementing indoor air quality (IAQ) programs. We administered a questionnaire on IAQ programs and practices to a representative sample of schools. Participants were asked to provide information on the use, administration, implementation, challenges, and benefits of the IAQ program in their school. We developed an IAQ Practice Index to determine the level of activity directed toward IAQ in schools. The index was computed based on responses to specific survey questions and was normalized to a range of 0 to 100. Each question was weighted qualitatively according to its contribution to strong IAQ management practices. Forty-two percent of schools in the United States have an IAQ management program, and there has been sustained growth from 1998 through 2002 in the number of schools that have such programs. Nearly half of those schools use the U.S. Environmental Protection Agency’s IAQ Tools for Schools program. The IAQ Practice Index scores varied widely for schools with an IAQ management program, suggesting that having a program is not equivalent to implementing effective IAQ policies and procedures. Respondents indicated that their IAQ programs led to improved workplace satisfaction, fewer asthma attacks, fewer visits to the school nurse, and lower absenteeism. When actively supported by the school administration, an IAQ program appears to be a valuable factor in improving the learning environment for U.S. schoolchildren.