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Traffic on a motorway. © INRA, MAITRE Christophe

Diesel engine air pollution: effects on foetuses for two generations

Peaks in fine-particulate air pollution are increasingly common and intense, and epidemiological data have shown that exposed pregnant women are at higher risk of having babies with low birth weight, which in turn can lead to the development of certain diseases such as metabolic syndrome. Initial findings from a research project* coordinated by INRA show that in animals, chronic exposure of pregnant mothers to exhaust from diesel engines fitted with a particulate filter (such as those in cars sold in Europe) lead to deleterious effects on the growth and metabolism of first- and second-generation foetuses. Scientists also have evidence, for the first time ever, that nanoparticles from inhaled diesel exhaust can cross the placenta and reach foetal blood.

Updated on 08/04/2016
Published on 07/28/2016

In order to study the effects of pollution - and in particular ultrafine particles and noxious gases (such as carbon monoxide and nitrogen oxide) present in exhaust from diesel engines in traffic in large cities - on the development of first- and second-generation foetuses and placentas, researchers observed gestating rabbits who inhaled filtered diesel engine exhaust  (containing only ultrafine particles and nanoparticles) at levels close to those that populations are exposed to on a daily basis during particulate-air pollution peaks in large European cities. Rabbits were chosen because their placentas are more similar to human placentas than those of model mice commonly used in experiments.

Halfway through gestation, signs of delayed foetal growth were observed. At full term, the length of the heads of foetuses was reduced, as was their waist size - the same observations made in humans. Ultrasounds showed a sharp decrease in blood flow to the placenta, reducing the supply of nutrients to the foetus.

Inhaled diesel nanoparticles reach the placenta

Using electron microscopy, researchers observed the presence of nanoparticles from diesel engine exhaust in the placenta and blood of foetuses.

The black clusters visible at the microvillus membrane of the placenta, the border where exchanges occur between mother and foetus, are accumulations of nanoparticles (transmission electron microscopy). © INRA, Josiane Aïoun
The black clusters visible at the microvillus membrane of the placenta, the border where exchanges occur between mother and foetus, are accumulations of nanoparticles (transmission electron microscopy) © INRA, Josiane Aïoun

Effects on second-generation foetuses

In adulthood, female rabbits born of exposed mothers were coupled with male rabbits who had never been exposed to this kind of pollution. No growth anomalies were found in their foetuses, but scientists did observe anomalies in the exchange of lipids between the mothers and the foetuses, illustrating the effects of exposure to pollution in the second generation.

Nowadays, particulate air pollution is becoming increasingly common and intense, because of the high number of diesel vehicles on European roads. Fine particles (diameter  >100 nanometres) are subject to regulations (information and alert thresholds) but nanoparticles (diameter <100 nanometres), which are also present in diesel engine exhaust, are not yet regulated. Pregnant women exposed to high concentrations of fine particles, corresponding to pollution peaks in big cities, are more at risk of having babies with growth retardation, that is, below normal size. It is a known fact that low-weight infants are generally at greater risk of developing cardiovascular diseases in adulthood, and scientific data show that it is possible there will also be effects on the second generation (grandchildren).   


*The project “Effects of atmospheric pollution on placental function and post-natal development” is financed by the French National Research Agency (ANR). Research also receives support from the European Commission within the framework of the European Research Council project “Environmentally-induced Developmental Origins of Health and Disease”.

This research is conducted by INRA, Inserm, the PremUp Foundation, University of Grenoble Alps, University Paris Sud and the Institute of Risk Assessment Sciences (University of Utrecht).

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Valentino et al. Maternal exposure to diluted diesel engine exhaust alters placental function and induces intergenerational effects in rabbits. Particle and Fibre Toxicology (2016) 13:39; DOI: 10.1186/s12989-016-0151-7