The island of Ireland enjoys relatively clear, fresh air because of the prevailing Atlantic winds and few dirty industries.  Yet cars and smoky coal fires, as well as emissions from some businesses and industries, continue to load our air with nitrogen oxide, polycyclic aromatic hyrdocarbons (PAHs), particulate matter (PM) and other substances.  There is no secret that breathing air filled with these pollutants is not healthy, especially for vulnerable populations such as the young and the aged.






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While PM10 has been decreasing in large urban areas, partly because of improved engine emissions, this reduction is not being achieved in smaller towns in Ireland that do not benefit from the ban on smoky coal.  Levels of PM2.5 in Ireland are generally low and Ireland is compliant with the limit values established under the Clean Air for Europe (CAFÉ) Directive.  However, all Member States of the European Union (EU) are required to calculate the current exposure of their population to PM2.5 and to take steps to reduce this exposure by 2020.   Ireland is required to reduce PM2.5 levels by 10% by 2020, a serious challenge in light of the prevalent sources for PM.





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As transport emissions continue to contribute over 20% of Ireland’s greenhouse gases (GHGs), they also continue to expose vulnerable populations to adverse health impacts.  Pregnant women constitute one class of vulnerable people and a recent comprehensive, international study has examined the risks to pregnant women from exposure to air pollution.

The Air Pollution Study and Low Birth Weights

The study involved 14 International Collaboration on Air Pollution and Pregnancy Outcomes (ICAPPO) centers in 9 countries and included over 3 million births generally occurring between late 1990s and mid 2000s. It is the largest multi-center study reporting on the association between air pollution and fetal growth using a common analytical protocol.

The researchers found that maternal exposure to particulate pollution — PM2.5 and PM10 — was associated with low birth weight (LBW) at term across study populations.  They concluded that each increase in PM10 by 10 micrograms per cubic meter (μg m–3) was associated with a 3% higher chance of an infant being underweight and with an overall average weight reduced by 3 grams.  Low birth weight is defined as a newborn baby weighing less than 2.5 kilograms (5.5 lbs). Not all the ICAPPO centers had measured for PM2.5, but of the seven that did the researchers found a slightly stronger relationship for maternal exposure to PM2.5 and effects on gestational growth than they did for PM10.

A major contribution is that the study eliminated, as far as possible, compounding factors that can influence LBW, such as smoking by parents and socio-economic status, and standardized the results across the 14 centers. It should be noted that, like many health studies, the results demonstrate an “association” between polluted air and LBW rather than “proving” that the polluted air causes the LBW.

In effect, there was an increased risk, however small, of low birth weight for increasing levels of particulate matter air pollution.  On an individual basis, the 3% increased risk is not very large, but for large communities, the public health effects can be widespread and deep.  Just think of Beijing, China.

The results confirm the adverse effects from air pollution, particularly in large urban environments, such as was found in the environmental disaster in London in 1952, and are consistent with studies of exposure of pregnant women to risks from toxic waste sites.

Other Air Pollution Incidents and Studies

London Fog 1952

In December 1952, thick, soot-laden air from the city’s household fires, and some industries, was trapped over London by a temperature inversion.  For five days, the air over the city was black and yellow, day became night, and everyone and everything was covered with soot.  Few realized just how deadly it was. After all, London had been notorious for its fog for a very long time. Romantic notions were attached to the fog, with events in many a thriller, period novel, and film set amidst fog-bound London. For the residents of London, the fog was a frequent, if unwelcome, guest who was becoming a bit of a nuisance.











But the combination of filthy air from coal fires and a temperature inversion was insidious. Those who suffered were the most vulnerable —the very young whose physical strength and defenses were as yet not fully formed, and the old whose biological systems were already breaking down.  The particulate matter and other contaminants that they inhaled simply overpowered their respiratory systems.

The London Fog of 1952 killed between 4,000 and 12,000 people.

Toxic Waste Sites

Studies of pregnant women living near toxic waste sites have found a strong association between proximity to the toxic wastes, with exposure through air or direct contact with soil, and LBW babies.  For example, at an infamous toxic waste site in New York, called Love Canal, over 20,000 tons of toxic chemical wastes were dumped in an unused canal by a chemical company in the 1940s and 1950s.   Early studies of the impacts from these toxic chemicals found that there was a positive association between women living along the canal during pregnancy and adverse reproductive outcomes, including low birth weight and congenital malformation.  New York State began a long-term study of the former residents of Love Canal to assess the health effects. An interim report in 2006 found that, consistent with the initial assessments, there was an association of low birth weight and prematurity to living close to the site.  In addition, the study found a higher ratio of female to male births among these women, noting a similar finding to those exposed to dioxins at Seveso, Italy.








These results were confirmed by a study of residents living near another infamous toxic waste site, the Lipari Landfill in New Jersey. This study found a significantly lower average birth weight among residents closest to the landfill, compared to the general population. These infants were also twice as likely to be born prematurely.

Another analysis of a number of studies of health effects from exposures to contaminants from landfills confirms the finding of a relationship between residential proximity to landfill sites and an increase in infants with low birth weights.

Health Effects

Even small associations between air pollution and LBW can be of major public health importance because of the ubiquitous nature of particulate air pollution exposure and the resulting potential for considerable population risks.  Again, think of Beijing where in January the 24-hour average reading for PM2.5 reached more than 460 μg m3 according to the US Embassy.  China reported a lower figure of around 350 μg m3.  For one comparison, using annual standards, the World Health Organization recommends that countries establish rigorous air-pollution standards of an annual mean of 10 μg m3 for PM2.5 and 20 μg m3 for PM10

There is long-standing evidence of both perinatal and lifelong effects of LBW on health, including increased risk of infection, hypoglycemia, hypoxia, feeding difficulties, behavioral problems. Later in childhood, and through adulthood, LBW infants can develop neurodevelopmental problems as well as increased risk of cardiovascular disease, diabetes, and other types of metabolic disorders.

Chinese mothers need to worry, as do any pregnant women exposed to PM and other pollutants from traffic or other sources.  The spouses and partners of all these women also need to worry.  Not to mention the children born with low birth weight from exposure to polluted air.



Payam Dadvand et al., “Maternal Exposure to Particulate Air Pollution and Term Birth Weight: A Multi-Country Evaluation of Effect and Heterogeneity,”  Environmental Health Perspectives.

“An Unlikely Duo: Air Pollution’s Link to Low Birth Weight, with Tracey Woodruff,” an Interview with one of the authors of the Dadvand et al. study, Environmental Health Perspectives (06 Feb 2013).

Hannah Hoag, “Air pollution delivers smaller babies,” Nature (06 Feb 2013).

See “Particulate Matter” in the iePEDIA section of irish environment (September 2009).

Environmental Protection Agency (RoI), Ireland’s Environment 2012: An Assessment, esp. Chapter 3 on “Air Quality”,33606,en.html

EPA, “EPA Ireland Archive of PM 2.5 Monitoring Data“. Associated datasets and digitial information objects connected to this resource are available at: Secure Archive For Environmental Research Data (SAFER) managed by Environmental Protection Agency Ireland (Last Accessed: 2013-02-15)

“Chinese struggle through ‘airpocalypse’ smog,” Guardian (16 Feb 2013)

See story of London Fog 1952 in Robert Emmet Hernan, This Borrowed Earth:  Lessons From the 15 Worst Environmental Disasters Around the World (Palgrave MacMillan, 2010; China Machine Press, 2011).

See story of Love Canal in Robert Emmet Hernan, This Borrowed Earth:  Lessons From the 15 Worst Environmental Disasters Around the World (Palgrave MacMillan, 2010; China Machine Press, 2011).

See Martine Vrijheid, “Health Effects of Residence Near Hazardous Waste Landfill Sites: A Review of Epidemiologic Literature,” Environmental Health Perspectives, 108(1), pp. 101-1 12 (2000).  Available at

Centers for Disease Control and Prevention (US), “Low Birthweight and the Environment”

Lifestrong, “The Effects of Low Birth Weight on Infants,”

NI Department of the Environment, “High Air Pollution Monitored in Parts of Northern Ireland” (20 Feb 2013)






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