Transport costs

By Priyanka Chandola
Published: Monday 15 June 2009

Traffic pollution is known to cause chronic bronchitis and asthma, killing thousands every year. But that is not all. Simply living beside a busy road has its consequences. Particles in vehicular exhaust can stick to lungs for longer than was known, endanger the health of an unborn child, lead to joint pains and even trigger male infertility

Stickier than glue
Smoke from a chulha or a wood fire can never cause as much damage as emissions resulting from traffic. A study shows tiny particles from traffic tend to stick to 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.The people were asked to stand on the sidewalk of a six-lane Copenhagen main road which has some 65,000 vehicles pass by everyday, 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 chambers 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 mainly stick to the mouth and throat," said Jakob Lndahl, from the department of physics at Lund University and the 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 that are deposited in the lungs is high because they are small, exist in high numbers and hence also have a large surface area," said Lndahl.

Examination of the nature of the particles further explained their strong 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 Lndahl. The water soluble 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 the March 24 online 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 Sandstrm, professor at Umea University, Sweden.

Foetal scare
Pregnant women might want to relocate to the countryside. Exposure to airborne traffic pollutants is adverse to foetal health. This, in turn, might have long-term implications such as retarded growth and respiratory stress in infants.

Researchers from the US examined the impact of pollutant concentrations on the weight of the foetus during different three-monthly phases or 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 United States 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 pipes of the lungs), 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 three categories: 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 as well maternal 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 the researchers in the study published in the April 8 online issue of the Journal of Epidemiology and Community Health.

In case of pregnancies with complications such as placental abruption (the placenta separates from the uterus wall before the baby's birth and leads to excessive bleeding), the risks of sga and vsga were found to increase two to five times. "Mothers developing such complications may be particularly susceptible to air pollution. But the results need to be confirmed," said researchers.

Blame the pain on traffic
Living near roads entails putting up with incessant traffic noise, air 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 women 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. Three types of roads--interstate, primary and secondary (multi-lanes)--were considered.

Women living within 50 metres of all types of streets were at a 31 per cent higher risk of incident rheumatoid arthritis compared to those living 200 metres away or further. "Even after accounting for the effects of age, race, gender, socioeconomic status and cigarette smoking, the risk for women located closer to major roads remained substantially higher," said Jaime Hart, at the Channing laboratory, and lead author of the study. For women living closest to the largest roadways (interstates) the risk jumped to 63 per cent.

"This is the first time an association has been demonstrated between rheumatoid arthritis and residential distance to the closest road," stated researchers in the study that appeared in the March 4 online issue of Environmental Health Perspectives.

Add vehicular pollution to the list of the risk factors linked to male infertility. A study in Kolkata--the third-most polluted city in the world in 2002 in terms of particulate pollution--suggests that certain parameters needed for efficient functioning of sperms are sensitive to the external environment. Male infertility, isolated or combined with female infertility, is a factor in about 50 per cent of cases where couples of reproductive age end up childless, said the study.

A total of 3,729 men were included in this two-decade long study (samples were taken between 1981-1985 and 2000-2006). The men had sperm count greater than 20 million per millilitre which according to who is the normal sperm count. But an examination of the sperm samples revealed a significant decline in semen volume and overall sperm motility in the 2000s compared to the 1980s. "Semen volume is regulated by the accessory sex glands. Environmental pollutants may have a detrimental effect on their functioning. Sperm motility is a parameter easily affected by the external environment," explained Alex C Varghese, chief embryologist at the Kolkata-based Advanced Medicare and Research Institute (amri) and an author of the study.

Researchers also examined the correlation of semen parameters with age in both decades. An annual decrease of 0.415 per cent in sperm motility with age was observed in the study population of the 2000s which was about 0.1 per cent higher than in the 1980s (0.314 per cent). This, the researchers contended, might be because of an increase in environmental pollution during the 2000s. Done jointly by researchers of amri, India and Cleveland Clinic, Ohio, usa, the study published online on March 27 in Fertility and Sterility.

Though the study has not directly evaluated the impact of polluted air of Kolkata with the change in various sperm parameters, statistics indicate the changes could be due to vehicular pollution.

The Nagpur-based National Environmental Engineering Research Institute (neeri) found an increased concentration of nitrogen oxides and carbon monoxide in the city's atmosphere during a survey (1970 to 2000). According to an emissions estimate calculated by neeri, transport emissions increased from 1,825 tonnes per annum in 1970 to 25,550 tonnes per annum in 1990. Diesel's contribution to PM2.5 in Kolkata is the highest among all Indian metros: 61 per cent.

Post 2000, the city had a large number of autorickshaws which increased the vehicular pollution manifold due to the use of katatel, a highly polluting mixture of solvent and kerosene, much cheaper than conventional fuels.

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