Silver Valley Lead Study: Further Analysis of the Relationship between Blood Lead and Air Lead

Blood lead and air lead levels of children who lived within 32 km of a smelter in Kellogg, ID were measured in 1974 and 1975. While an analysis of the 1974 survey has appeared, the results of the 1975 survey and an evaluation of the change in blood lead levels of those children who participated in both the 1974 and 1975 surveys has not previously been discussed in the literature. It Is concluded that, for these data, in the air lead range of 0.5–5 μg/m³, the blood lead-air lead relationship can be adequately described by blood lead-air lead slope which is approximately 1.0 and at most 1.4. This slope was also found to be Independent of children’s age. It Is shown that an accurate estimate of the blood lead-air lead relationship cannot be obtained without taking proper account of selected environmental variables; specifically, pica, sex, age, father’s work status, education, and home cleanliness.     

Fly Ash from Electrostatic Precipitators: Characterization of Large Spheres

The body of information contained in this paper is directed towards individuals concerned with the toxicology and physical state of airborne effluents from pulverized coal-fired stationary sources. A flotation/sedimentation technique was used to separate fly ash from power plant clean-up devices into light, medium, and high density fractions. Large spherical particles were selected from each fraction and examined by optical and scanning electron microscopy. Attempts were made to identify pleurospheres (filled hollow spheres) by crushing the spheres in situ under the optical microscope. In no cases were filled spheres observed, suggesting that they are not a common structure in fly ash. Several phenomena which generate hollow spheres are discussed.     

Relationships between Aerosol Extinction Coefficients Derived from Airport Visual Range Observations and Alternative Measures of Airborne Particle Mass

Epidemiological assessments of population exposures to airborne particles are often hampered by the scarcity of available fine particle mass measurements. In an attempt to overcome this serious problem, we analyze In this paper methods for predicting fine particle (M ₁) and Inhalable particle (IP) mass concentrations using relative humidity corrected light extinction coefficient (b _ext) estimated from airport visual range (V _r) observations. The analyses presented are based on theoretical determinations as well as statistical investigations utilizing EPA's NASN and Inhalable Particle Monitoring Network (IPMN) data bases and routine airport visual range observations In twelve large U.S. cities. Our results Indicate that, after controlling for certain limitations of airport visual range data, most of the regression models developed in this paper can be applied satisfactorily to predict M _t and IP. Furthermore, our findings Indicate that a more representative formula than the commonly used meteorological range formula to predict atmospheric b _ext values in urban areas may be b _ext = (1.8 ± 0.04)/V _r. Because of known local or regional influences, however, we do suggest calibration of any predictive model which utilizes airport visibility data against site-specific aerometric data on particle mass concentrations or scattering coefficient measurements.     

Performance Evaluation of Integral and Analytical Plume Rise Algorithms

The purpose of this study was to evaluate the performance of current regulatory algorithms for predicting plume rise for refinerytype sources (short stacks and a wide range of source conditions) and the performance of new or alternate algorithms which may provide better estimates. To meet the objectives, five plume rise algorithms were statistically evaluated against ten field and laboratory plume rise data bases. Two forms of the Briggs plume rise equations were tested because they are almost exclusively used in current EPA regulatory models. Two modified Briggs equations were tested to assess how simple modifications can Improve the accuracy of the estimates. The fifth algorithm was a numerical solution to the basic equations for conservation of mass, momentum, and energy often referred to as an Integral plume rise algorithm. This algorithm was selected because It handles the wide range of source and atmospheric boundary-layer conditions that affect trajectories of plumes from refinery stacks.

Ten independent plume rise data bases were assembled that covered a wide range of source and meteorological conditions. From the data bases, a total of 107 different data sets were obtained and each data set included plume rise observations versus downwind distance for one source and meteorological condition. Each model was run for each data set and the root-mean-square and mean error between model and observation was computed for use in statistically evaluating model performance.

The statistical evaluation of the algorithms showed that the rms error (considering all data bases) for the Integral plume rise algorithm was approximately 30 percent less than the errors for all other algorithms tested. This difference was significant at the 95 percent confidence level. The results suggest that improved plume rise estimates in regulatory models applied to refineries and other appropriate sources could be achieved to reduce costs and improve ambient air quality estimates through the use of an integral plume rise algorithm.     

Health Risks of Short-term S02 Exposure to Exercising Asthmatics

A method is described for quantifying health risks to asthmatics briefly exposed to elevated levels of SO₂. By combining symptomologlcal and physiological measurements, we have developed a dose-response surface that relates both severity and incidence of response to ambient air quality levels. The complete model to assess potentially avoidable risks includes power plant emission data; ambient SO₂ background levels; demographic and activity patterns of asthmatics, the identified population at risk; and the dose-response surface. The estimated annual risk to persons experiencing an SO₂-lnduced response due to a nearby power plant is quite small (response rates under 3 percent). Uncertainties due to modeling errors, variations in activity patterns, demographics and physiological response are discussed.     

Soil Remediation Techniques at Uncontrolled Hazardous Waste Sites

The A&WMA Critical Review entitled “Soil Remediation Techniques at Uncontrolled Hazardous Waste Sites” was presented by Ronald C. Sims, Department of Civil and Environmental Engineering, Utah State University, Logan, Utah. Dr. Sims presented his review at the 83rd Air & Waste Management Association Annual Meeting, held in Pittsburgh, Pennsylvania in June 1990. Prepared discussions presented during the Critical Review session are published here, along with some closing remarks by Dr. Sims. Ronald Harkov, Chairman of the Critical Review Subcommittee of the Publications Committee, served as moderator of the 1990 A&WMA Critical Review session.     

Formaldehyde,Melhanol and Hydrocarbon Emissions from Methanol-fueled Cars

Exhaust and evaporative emissions tests were conducted on several methanol- and gasoline-fueled vehicles. Separate samples for chromatographlc analysis of formaldehyde, methanol, and Individual hydrocarbons were collected in each of the three phases of the driving cycle and in each of the two portions of the evaporative emissions test. One vehicle, equipped with an experimental variable-fuel engine, was tested using methanol/gasoline fuel mixtures of 100, 85, 50,15, and 0 percent methanol. Combustion-generated hydrocarbons were lowest using methanol fuel, and increased several-fold as the gasoline fraction was increased. Gasoline components In the exhaust Increased from zero as the gasoline fraction of the fuel was Increased. On the other hand, formaldehyde emissions were several times higher using methanol fuel than they were using gasoline. A dedicated methanol car and the variable-fuel car gave similar emissions patterns when they both were tested using methanol fuel. The organic-carbon composition of the exhaust was 85-90 percent methanol, 5-7 percent formaldehyde, and 3-9 percent hydrocarbons. Several cars that were tested using gasoline emitted similar distributions of hydrocarbons, even through the vehicles represented a broad range of current and developmental engine families and emissions control systems. These vehicles continue the trend of the past twenty years toward less photochemically reactive exhaust, with higher percentages of methane and total alkanes, and correspondingly lower percentages of oleflns and aromatlcs.     

Field Measurements of Particulate Matter Emissions,Carbon Monoxide,and Exhaust Opacity from Heavy-Duty Diesel Vehicles

ABSTRACT

Diesel particulate matter (PM) is a significant contributor to ambient air PM₁₀ and PM_2.5 particulate levels. In addition, recent literature argues that submicron diesel PM is a pulmonary health hazard. There is difficulty in attributing PM emissions to specific operating modes of a diesel engine, although it is acknowledged that PM production rises dramatically with load and that high PM emissions occur during rapid load increases on turbocharged engines. Snap-acceleration tests generally identify PM associated with rapid transient operating conditions, but not with high load. To quantify the origin of PM during transient engine operation, continuous opacity measurements have been made using a Wager 650CP full flow exhaust opacity meter. Opacity measurements were taken while the vehicles were operated over transient driving cycles on a chassis dynamometer using the West Virginia University (WVU) Transportable Heavy Duty Vehicle Emissions Testing Laboratories. Data were gathered from Detroit Diesel, Cummins, Caterpillar, and Navistar heavy-duty (HD) diesel engines. Driving cycles used were the Central Business District (CBD) cycle, the WVU 5-Peak Truck cycle, the WVU 5-Mile route, and the New York City Bus (NYCB) cycle. Continuous opacity measurements, integrated over the entire driving cycle, were compared to total integrated PM mass. In addition, the truck was subjected to repeat snap-acceleration tests, and PM was collected for a composite of these snap-acceleration tests. Additional data were obtained from a fleet of 1996 New Flyer buses in Flint, MI, equipped with electronically controlled Detroit Diesel Series 50 engines. Again, continuous opacity, regulated gaseous emissions, and PM were measured. The relationship between continuous carbon monoxide (CO) emissions and continuous opacity was noted. In identifying the level of PM emissions in transient diesel engine operation, it is suggested that CO emissions may prove to be a useful indicator and may be used to apportion total PM on a continuous basis over a transient cycle. The projected continuous PM data will prove valuable in future mobile source inventory prediction.     

Diagnostics for Determining Influential Species in the Chemical Mass Balance Receptor Model

ABSTRACT

The chemical mass balance (CMB) model can be applied to estimate the amount of airborne particulate matter (PM) coming from various sources given the ambient chemical composition of the particles measured at the receptor and the chemical composition of the source emissions. Of considerable practical importance is the identification of those chemical species that have a large effect on either the source contributions or errors estimated by the CMB model. This paper details a study of a number of influential diagnostics for application of the CMB software. Some of the diagnostics studied are standard regression diagnostics based on single-row deletion diagnostics. A number of new diagnostics were developed specifically for the CMB application, based on the pseudo-inverse of the source composition matrix and called nondeletion diagnostics to distinguish them from the standard deletion diagnostics. Simulated data sets were generated to compare the diagnostics and their response to controlled amounts of random error.

A particular diagnostic called a modified pseudoinverse matrix (MPIN), developed for this study, was found to be the best choice for CMB model application. The MPIN diagnostic contains virtually all the information present in both deletion and nondeletion diagnostics. Since the MPIN diagnostic requires only the source profiles, it can be used to identify influential species in advance without sampling the ambient data and to improve CMB results through possible remedial actions for the influential species. Specific recommendations are given for interpretation and use of the MPIN diagnostic with the CMB model software. Elements with normalized MPIN absolute values of 1 to 0.5 are associated with influential elements. Noninfluential elements have normalized MPIN absolute values of 0.3 or less. Elements with absolute values between 0.3 and 0.5 are ambiguous but should generally be considered noninfluential.     

Dissociation of Sulfur Hexafluoride Tracer Gas in the Presence of an Indoor Combustion Source

ABSTRACT

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 ~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.