City Smog Research Articles

Controlling automotive exhaust emissions: successes and underlying science

Photochemical reactions of vehicle exhaust pollutants were responsible for photochemical smog in many cities during the 1960s and 1970s. Engine improvements helped, but additional measures were needed to achieve legislated emissions levels. First oxidation catalysts lowered hydrocarbon and carbon monoxide, and later nitrogen oxides were reduced to nitrogen in a two-stage process. By the 1980s, exhaust gas could be kept stoichiometric and hydrocarbons, carbon monoxide and nitrogen oxides were simultaneously converted over a single 'three-way catalyst'. Today, advanced three-way catalyst systems emissions are exceptionally low. NOx control from lean-burn engines demands an additional approach because NO cannot be dissociated under lean conditions. Current lean-burn gasoline engine NOx control involves forming a nitrate phase and periodically enriching the exhaust to reduce it to nitrogen, and this is being modified for use on diesel engines. Selective catalytic reduction with ammonia is an alternative that can be very efficient, but it requires ammonia or a compound from which it can be obtained. Diesel engines produce particulate matter, and, because of health concerns, filtration processes are being introduced to control these emissions. On heavy duty diesel engines the exhaust gas temperature is high enough for NO in the exhaust to be oxidised over a catalyst to NO2 that smoothly oxidises particulate material (PM) in the filter. Passenger cars operate at lower temperatures, and it is necessary to periodically burn the PM in air at high temperatures.

Using Science to Advocate Action on Climate Change

ABSTRACT Climate change is probably the greatest threat to global ecosystems that humanity has ever faced. Greenhouse gases, primarily from the production and combustion of fossil fuels for human energy needs, are heating up our atmosphere, changing our climate, and threatening the health and well‐being of people the world over. Predicted consequences of climate change include more frequent extreme weather events such as intensive precipitation, drought and floods, rising sea levels, increased smog in cities, and the possible spread of tropical diseases to more temperate climes. These grim effects can be limited if societies throughout the world act quickly to reduce greenhouse gas emissions. Substantially reducing emissions, however, means a fundamental shift in the way we produce and consume energy. To help bring about change, scientists, health professionals and nongovernment organizations such as the David Suzuki Foundation must work together to educate and motivate the public, industries, business organizations, and governments to take actions that will reduce the threat of global warming.

Endangered Mexico: an environment on the edge

In this work, the author makes it clear that there is more to Mexico's environment than city smog. This book gives an account of the whole range of environmental problems which face Mexico's people, from tourist development to oil spills and land exhaustion.

New Source Identified for Mexico City Smog

New Source Identified for Mexico City Smog

Evaluation of health risks by airborne particulates from in vitro cyto- and genotoxicity testing on human and rodent tissue culture cells: A longitudinal study from 1975 until now

Airborne particulate matter or city smog from heavily industrialized regions contains more than 600 mostly organic chemical substances, among them also potential carcinogens and mutagens. 41 samples of airborne particulate matter were collected between 1975 and 1990 at various locations of the highly industrialized Rhine-Ruhr region in F.R.Germany. Extracts of airborne particulates were prepared by organic solvents. Results demonstrate pronounced cytotoxic, mutagenic and carcinogenic activities of various samples of airborne particulates. Cytotoxicity testing of samples revealed a gradual dose-related impairment of phagocytosis of human and rodent macrophages leading at higher concentrations to a loss of cell viability. We observed a dose-dependent reduction of “plating efficiency” of human and rodent cell lines. Genotoxic activity of extracts was demonstrated by a dose-related induction of “sister chromatid exchanges” in human lymphocyte cultures. Furthermore, we found a pronounced dose-dependent “enhancement” of neoplastic cell transformation of Syrian hamster kidney cultures infected with Simian virus (SV-) 40.

Comparative Investigation of Carcinogenic and Mutagenic Activity of Airborne Particulate Matter from Polluted Areas Using Human and Rodent Tissue Culture Cells

Extract of airborne particulate matter or city smog from the highly industrialized Rhine–Ruhr region (F.R.G.) contains chemical substances which exert mutagenic and carcinogenic activity on mammalian cells in vitro. Mutagenic effects were demonstrable by induction of ‘sister chromatid exchanges’ in human lymphocyte cultures and Chinese hamster at the HGPRT*-Locus in V 79 cells. Carcinogenicity was shown by enhancement of malignant cell transformation of Syrian hamster kidney cultures infected with Simian Virus (SV-) 40. Results obtained with mutagenicity and carcinogenicity tests revealed a high significant dose-effect relationship. Taking into consideration a human respiratory volume of 12–14 cbm of air per day, quantities of extract of city smog no. 18, equivalent to air volumes of 0.5–1 cbm, showed mutagenic and carcinogenic activity.

Comparative investigation on the genotoxicity of city smog and automobile exhaust particulates

Comparative investigation on the genotoxicity of city smog and automobile exhaust particulates

Cytogenetic effects of airborne particulate matter in human lymphocytes in vitro

City smog was collected in a heavily industrialized area and investigated for its ability to induce cytogenetic effects in human lymphocytes in vitro. Total extract of city smog was found to produce sister-chromatid exchanges and chromosomal aberrations in a dose-dependent manner. In addition cell-cycle delay was observed at higher concentrations of city smog extract. Results of cytogenetic testing are discussed with respect to cell-cycle kinetics.

Demonstration of carcinogenic and mutagenic activity of airborne particulates (city smog) from polluted area using human and rodent tissuf culture cells

Demonstration of carcinogenic and mutagenic activity of airborne particulates (city smog) from polluted area using human and rodent tissuf culture cells

Cell transformation in vitro by city smog extracts and fractions

Cell transformation in vitro by city smog extracts and fractions

“Sister-chromatid exchanges” induced by city smog extracts and fractions in cultured human lymphocytes

We use the statistics of a large and curated training set of transmembrane helical proteins to develop a knowledge-based potential that accounts for the dependence on both the depth of burial of the protein in the membrane and the degree of side-chain exposure. Additionally, the statistical potential includes depth-dependent energies for unsatisfied backbone hydrogen bond donors and acceptors, which are found to be relatively small, ∼2 RT. Our potential accurately places known proteins within the bilayer. The potential is applied to the mechanosensing MscL channel in membranes of varying thickness and curvature, as well as to the prediction of protein structure. The potential is incorporated into our new Upside molecular dynamics algorithm. Notably, we account for the exchange of protein-lipid interactions for protein-protein interactions as helices contact each other, thereby avoiding overestimating the energetics of helix association within the membrane. Simulations of most multimeric complexes find that isolated monomers and the oligomers retain the same orientation in the membrane, suggesting that the assembly of prepositioned monomers presents a viable mechanism of oligomerization.

Analysis of cytotoxic effects of city smog extracts and fractions on cells in vitro

Analysis of cytotoxic effects of city smog extracts and fractions on cells in vitro

Induction of “sister-chromatid exchange” by city smog extracts and their fractions in cultured human lymphocytes

Induction of “sister-chromatid exchange” by city smog extracts and their fractions in cultured human lymphocytes

Cytotoxic effects of air pollutants on mammalian cells in vitro

Extract and fractions of city smog collected from a heavy industrialized area caused in vitro dose-dependent reduction of cell survival of mouse macrophages and a growth inhibition of human fetal diploid lung fibroblasts Great differences were observed in both cell systems between the total extract and its different fractions. Cytotoxicity declined in the sequence of total extract followed by fractions of cyclohexane, methanol, propanol and of polycyclic aromatic hydrocarbons. Our results illustrate that samples of city smog contain highly toxic substances for mammalian cells in vitro. Differences in cytotoxicity of particular fractions indicate that toxic agents belong to various classes of chemical substances.

Transformation of rat and hamster embryo cells by extracts of city smog.

Extracts of particulate matter from condensates of city air were tested for their ability to transform rat or hamster cell cultures. Uninfected rat embryo cultures were not transformed, but cultures chronically infected with Rauscher leukemia virus were transformed by benzpyrene or by extracts of city smog. The smog extracts were 600 times more active than pure benzpyrene as transforming agents. Hamster embryo cultures infected with hamster leukemia virus were equally as sensitive as leukemia-infected rat cultures to the transforming effects of smog; uninfected hamster cultures were also transformed, although tenfold higher doses of smog extract were required.

The Decrease of the Ultraviolet Solar Radiation by City Smog Occurring in Winter

The Decrease of the Ultraviolet Solar Radiation by City Smog Occurring in Winter