Biotechniques for air pollution control

This paper gives an overview of present biological techniques for the treatment of off-gases and the techniques that are being developed at the moment. The characteristics, advantages, disadvantages, costs and application area are discussed and compared. Biological off-gas treatment is based on the absorption of volatile contaminants in an aqueous phase or biofilm followed by oxidation by the action of microorganisms. Biofilters, bioscrubbers and biotrickling filters are used for elimination of odour and bioconvertable volatile organic and inorganic compounds and are enjoying increasing popularity. This popularity is a result of the low investment and operational costs involved compared to physico-chemical techniques and the elimination efficiencies that can be obtained. The operational envelop is still extending to higher concentrations and gas flow rates (exceeding 200,000 m³ h^–1) and a broader spectrum of degradable compounds. Research and development on the use of membranes and the addition of activated carbon or a second liquid phase to the biological systems may lead to a more efficient elimination of hydrophobic compounds and buffering of fluctuating loads. Shorter adaptation periods can be obtained by inoculation with specialized microorganisms. Improved design and operation are made possible by the growing insights in the kinetics and microbiology and supported by the development of models describing biological off-gas treatment. In conclusion, biotechniques are efficient and cost effective in treating off-gases with concentrations of biodegradable contaminants up to 1–5 g/m³. They could play a justified and important role in air pollution control in the coming years.Abbreviations VOC volatile organic compound - NO _x gaseous oxides of nitrogen     

Perspectives in chronobiology of air pollution

In a series of experiments, male and female Sprague Dawley rats, kept in light (L) from 06(00) to 18(00) alternating with darkness (LD 12:12) inhaled different concentrations of carbon monoxide (50-1,700 ppm) at each of two test times, 12 h apart. A decrease in flow of CO2 (VCO2) resulting from CO inhalation was greater in the active dark (D) than resting light (L) span. Experimental hypoxic mortality of male and female mice also shows circadian variations, being greater in the D than in the L span. Moreover, a difference of mortality was observed betwen hypoxic exposures performed at 12(00) (in LD or DL) and hypoxic exposures performed at 00(00) (in LD or DL). Such results await tests of any extent to which they model responses of human beings to air pollution. In human beings any external environmental circadian, circaseptan and circannual variations in air pollution as such may serve to variable extent as socioeconomic synchronizers of innate rhythms with a corresponding frequency, rather than as solely generators of time patterns in any physiopathologic response to air pollution.     

External air pollution costs of telework

Background, Aims and Scope  Telework is associated with a number of costs and benefits, including reduced company overhead costs, need for office and parking space, office energy consumption, increased productivity, reduced absenteeism, retention of specialized employees, reduction in transportation-related fuel consumption and air pollution, and many others. This paper applies a systems model to telework and nontelework scenarios to quantify direct energy and fuel costs and external costs related to air emissions from transportation, heating, cooling, lighting, and electronic and electrical equipment use both at the company and the home office, including rebound effects. Methods  E-COMMUTair, a scalable web-based tool created by the authors and designed to assess the air pollution effects of individual or company telework programs versus nontelework is employed along with Monte Carlo simulation and sensitivity analysis. E-COMMUTair is using the latest available U.S. energy use and air emission factors. The external costs of air emissions are estimated. The role of telecommuting frequency is emphasized, and differences between various states are explored. The paper identifies the drivers of external costs, and presents an example breakeven analysis focused on CO₂ and key model parameters. Results and Discussion  Nontelework’s external costs are equal to or higher than telework’s costs for every model component, demonstrating that telework programs could provide benefits, including monetary benefits, to society. Transportation is the major contributor to the total costs, with home heating and cooling, and office cooling following. Most of the monetary costs associated with transportation are borne by individuals rather than society. Teleworking employees increase their home-related expenses but reduce their travel-related expenses, ending up with smaller total costs. Energy and fuel costs get reduced in the office space when telework programs are applied, resulting in benefits to companies. Energy and external costs decrease as telework frequency increases. When compared to not teleworking, 5-day telework scenarios on cooling days in California can have about 50–70% lower total costs. The probabilistic analysis confirms the results of the deterministic analysis. The sensitivity analysis reveals that for the nontelework scenario, transportation-related variables such as commuting distance and average number of passengers affect CO₂, CO, and NO_x emissions, while for the telework part, frequency and the number of roundtrips are the most relevant. Conclusions  Both analyses show that telework programs have the potential to lower both energy and external costs creating a favorable bottom line for society, employees, and companies by decreasing tailpipe emissions, lowering transportation costs, and decreasing energy costs at the company office. However, important parameters such as telecommuting frequency, characteristics of the office and home space, climate patterns, and rebound effects that determine external costs along with the price of gasoline, electricity and natural gas in the state where the program is implemented can greatly influence the final results, and should be carefully examined. Recommendations and Perspectives  The effects of telework programs on people’s daily lives are complex and difficult to predict and quantify. The current analysis showed that significant financial benefits can be expected from telework programs, but as seen often in environmental policy-making, the details of implementation will make or break the success of a program. formerly Postdoctoral Researcher, University of California, Berkeley ESS-Submission Editor: Dr. Gerald Rebitzer (Gerald.Rebitzer@alcan.com)     

Traffic air pollution and oxidized LDL

Background

Epidemiologic studies indirectly suggest that air pollution accelerates atherosclerosis. We hypothesized that individual exposure to particulate matter (PM) derived from fossil fuel would correlate with plasma concentrations of oxidized low-density lipoprotein (LDL), taken as a marker of atherosclerosis. We tested this hypothesis in patients with diabetes, who are at high risk for atherosclerosis.

Methodology/Principal Findings

In a cross-sectional study of non-smoking adult outpatients with diabetes we assessed individual chronic exposure to PM by measuring the area occupied by carbon in airway macrophages, collected by sputum induction and by determining the distance from the patient''s residence to a major road, through geocoding. These exposure indices were regressed against plasma concentrations of oxidized LDL, von Willebrand factor and plasminogen activator inhibitor 1 (PAI-1). We could assess the carbon load of airway macrophages in 79 subjects (58 percent). Each doubling in the distance of residence from major roads was associated with a 0.027 µm² decrease (95% confidence interval (CI): −0.048 to −0.0051) in the carbon load of airway macrophages. Independently from other covariates, we found that each increase of 0.25 µm² [interquartile range (IQR)] in carbon load was associated with an increase of 7.3 U/L (95% CI: 1.3 to 13.3) in plasma oxidized LDL. Each doubling in distance of residence from major roads was associated with a decrease of −2.9 U/L (95% CI: −5.2 to −0.72) in oxidized LDL. Neither the carbon load of macrophages nor the distance from residence to major roads, were associated with plasma von Willebrand factor or PAI-1.

Conclusions

The observed positive association, in a susceptible group of the general population, between plasma oxidized LDL levels and either the carbon load of airway macrophages or the proximity of the subject''s residence to busy roads suggests a proatherogenic effect of traffic air pollution.