Trouble with traffic

Smoke from a chulha or a wood fire can never cause as much damage as emissions resulting from traffic. A study shows that tiny particles from traffic tend to stick to the lungs for longer periods than other smoke and dust particles.

Researchers from the Lund University, Sweden, measured the amount of airborne particles from vehicular exhaust that stayed back in the lungs of nine healthy individuals.

They were asked to stand on the sidewalk of a six-lane Copenhagen main road which has 65,000 vehicles pass by daily, and breathe into a new two-chambered device called the RESPI. Air was inhaled through one chamber and exhaled through another. The concentration of particles in both was measured. The difference between the two gave the concentration of the particles that got stuck to the lungs.

“A large part of the traffic exhaust particles are in the ultrafine range. These have a high tendency to deposit in the deep parts of the lungs. The very big particles stick to the mouth and throat,” said Jakob Löndahl, from the department of physics at Lund University and lead researcher of the study. The team compared the deposition of particles from traffic emissions with particles originating from biomass combustion measured in a previous study.

The results indicated that for 100 microgramme per cubic metre of particles inhaled in one hour, the number of traffic particles that were retained was 16 times the biomass particles. “The total number of traffic particles deposited in the lungs is high because they are small, exist in high numbers and also have a large surface area,” said Löndahl.

Examination of the nature of the particles further explained their tendency to deposit in the lungs. Particles in vehicular exhaust have oily characteristics because of the presence of diesel and that makes them hydrophobic (water-repelling). Biomass contains salts, which make the particles water soluble, said Löndahl. The particles dissolve and are relocated to secondary organs like the gastrointestinal tract but the hydrophobic particles stay back for hours, said the study published in a recent issue of Environmental Science and Technology. “This explains why emissions from vehicles running on diesel are linked to high toxicity risk leading to increased chances of heart disorders,” said Thomas Sandström, professor at Umea University, Sweden.

Exposure to airborne traffic pollutants is adverse to foetal health.

Fertility and pollution
Researchers from the US examined the impact of pollutant concentrations on the weight of the foetus during different trimesters of pregnancy. The team obtained information on all singleton babies born in New Jersey, USA, to mothers who were New Jersey residents at the time of birth between 1999 and 2003. The areas of residence were mapped according to their distance from the nearest particulate matter monitoring station.
 
The US Environmental Protection Agency provided data for pollutants which included PM2.5 (particulate matter of diameter less than 2.5 micron and small enough to enter even the smallest lung pipes), nitrogen dioxide, sulphur dioxide and carbon monoxide.

An infant’s birth weight is linked to weight of the foetus. Low birth weight is a risk factor and is defined as less than 2.5 kg. Very low birth weights are less than 1.5 kg. Based on these, the team classified the foetal weights under: very small for gestational age (VSGA), small for gestational age (SGA) and normal for gestational age.

In case of PM2.5, only those cases were included in the study who resided within 10 kms of the nearest particulate matter monitoring station. The risk of SGA was found to increase with each four microgramme per cubic metre rise in PM2.5 concentration during the first and third trimesters.

An increase in 10 ppb (parts per billion) of nitrogen dioxide concentrations increased the risk of VSGA significantly in all three trimesters. No link was found between sulphur dioxide and carbon monoxide concentrations and risks of either SGA or VSGA.

Considering other risk factors which included smoking and alcohol use and characteristics like age, race and education, the team found that mothers of SGA and VSGA newborns were more likely to be younger, less educated, of Afro-American ethnicity, smokers, and single parents as compared to mothers with normal birth weight babies.

These risk factors notwithstanding, the ambient air pollutants still played a major role in restricting foetal growth, said researchers in the study published in the Journal of Epidemiology and Community Health.

Busy roads and arthritis
Living near roads entails putting up with incessant traffic noise, pollution and now, a research says, rheumatoid arthritis. This is an autoimmune disease that causes painful inflammation of the joints and other organs. The common risk factors are age, cigarette smoking and reproductive history. Now the distance between your home and the nearest street will also count.

Researchers from the Channing laboratory at Brigham and Women’s Hospital, Boston, USA, studied records of women who were enrolled in a nurses’ health study initiated in 1976. Of the 121,700 US registered female nurses, 90,297 who did not have a history of rheumatoid arthritis or cancer were included in the analysis. The team used geographical information software to measure the distance between a nurse’s home and the nearest road.

Women living within 50 metres of all types of streets were at a 31 per cent higher risk of rheumatoid arthritis compared to those living 200 metres away or further. “This is the first time an association has been demonstrated between rheumatoid arthritis and residential distance to the closest road,” said researchers in the study in a recent issue of Environmental Health Perspectives.
Down To Earth Feature Service