Even Foetuses Are Harmed By Air Pollution

Main Category: Pediatrics / Children's Health
Also Included In: Water - Air Quality / Agriculture;  Respiratory / Asthma
Article Date: 07 Oct 2008 - 3:00 PST

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When a pregnant woman breathes polluted air, the foetus suffers too. So concludes a Swiss study, presented in Berlin at the Annual Congress of the European Respiratory Society (ERS), which shows for the first time that, when a mother to-be is exposed to pollution, her baby is also affected, and the newborn's breathing will reflect this impact.

Exposing children to air pollution was known to impair their lung development at school age. What had not been recognised was the degree to which exposing a pregnant woman to pollution could affect the developing lungs of the foetus.

So Philipp Latzin and coworkers from the University of Bern (Switzerland) set out to assess prospectively the impact of air pollution on lung development in 241 newborns.

First, the researchers obtained measurements of the day-to-day quality of the air that the mothers breathed during their pregnancies. They analysed levels of three indicators of atmospheric pollution: ozone (O₃), nitrogen dioxide (NO₂) and airborne particulate matter of less than 10 micrometres in diameter (PM10).

They also considered the distance between the mother's home and major roads. Finally, the team assessed the respiratory function during sleep of full-term babies when they reached five weeks of age.

Pollution increases respiratory needs

As Latzin told the Congress, PM10 exposure during pregnancy appears to cause changes in the newborn's respiratory parameters. The more polluted the air, the greater the increase in respiratory frequency, tidal flows and minute volume.

For each 1µg/m3 increase of mean PM10 in the air breathed by the mother during pregnancy, the newborn's respiration increased by an average of 24.9 ml/min. The increase was even greater (39.2 ml/min) when the mother lived less than 150 metres from a road at least six metres wide, considered to be a major road.

In comparison to newborn children of mothers who had suffered less exposure, the most exposed babies breathed on average 48 times per minute instead of 42 times.

So babies' respiratory needs increase following such pollution exposure.

"This observation may be clinically significant, particularly for newborns who already have a reduced respiratory capacity or who are seriously unwell", the authors emphasised.

Stronger inflammatory reaction

The results presented in Berlin also show that antenatal NO₂ exposure is associated with a significant rise in exhaled nitric oxide (eNO), a marker of airway inflammation. Each 1µg/m3 rise in mean NO2 during pregnancy is associated with a 0.98ppb increase in eNO in the newborns.

Thus, a newborn with prenatal exposure to air pollution presents both greater respiratory needs and a stronger degree of airway inflammation. These changes are particularly marked where the higher exposure of the mothers took place during the third trimester of pregnancy.

All of these results were confirmed after adjustment for possible bias arising from postnatal exposure to atmospheric pollution as well as other factors including season of birth, outdoor temperature and socio-economic status.

As to the mechanisms that could explain the Swiss team's discovery, the study presented to the Congress did not seek to identify them. However, Latzin does have some suggestions.

According to him, one possibility might be that oxidative stress and inflammation in the mother's lungs may reduce blood flow to the placenta, where exchange takes place between the mother's blood and that of the foetus, thus reducing nutrient supply.

Pollutant particles might also act directly by entering the foetal bloodstream and reducing respiratory rhythm. Or they could act on the mother's metabolism and reduce the production of growth factors, potentially impacting on the formation of pulmonary alveoli.

Only one solution: improve air quality

Pollution thus has a considerable impact at a very early stage in lung development. This links in with the now highly fashionable "Barker hypothesis", according to which influences experienced in the womb have a long-term impact on each individual's health.

If this hypothesis is true, "these early influences on the respiratory system will lead to an increase in lung disease in adulthood and reduce life expectancy" the authors suggest.

"Hence, our results are further evidence for a need to strengthen atmospheric pollution reduction measures", they concluded in Berlin.

On Sunday, October 5, Philipp Latzin was awarded one of the ERS Annual Awards for Paediatric Respiratory Research in Europe.

European Respiratory Society

European Respiratory Society Annual Congress