If you could choose where to live in cities such as São Paulo, Rio de Janeiro or even Porto Alegre, it would be better to opt for a house or apartment as far away as possible – at least two blocks – from the busiest streets and avenues. It will be good for your and your children’s health. The reason is that the pollutants emitted by car, bus and truck engines usually spread out over a radius of up to 150 meters from the point at which they are launched into the air, and turn the major thoroughfares, such as Avenida Paulista or Avenida 23 de Maio, in the city of São Paulo, through which tens of thousands of vehicles pass each day, into immense chimneys that dump tons of toxic particles and gases onto the city.
The most immediate – and moderate consequences – of filling your lungs every single day with the almost unbreathable air of the major cities are soon visible: irritation in the eyes and breathing passages, a feeling of being unwell and asthma attacks. Other more serious consequences, which slowly gain a hold in the organism, such as an increase in blood pressure and the occurrence of cardiac arrest, can go unnoticed because they do not always show such a clearly direct link with this environmental factor.
However, it has become increasingly evident that air pollution does not affect only those who breathe it. Years ago, doctor Nelson Gouveia, from the University of São Paulo (USP), analyzed data for 214 thousand children who had been born in the state of São Paulo’s capital and came to the conclusion that exposure of pregnant women to this type of pollution, particularly during the first three months of the pregnancy, leads to lower baby weights at the time of birth. And this is one of the main determinants of infants’ health. Now he has estimated, although indirectly, another effect on newborns, due to the pollution breathed in by pregnant women: an increase in the risk of death during the first days following birth.
Taking into account the flow of vehicles in the streets of São Paulo as measured by the Traffic Engineering Company (CET) at rush hour and the distance at which these women lived from the city’s busiest streets and avenues, Gouveia, together with another doctor, Andréa Peneluppi Medeiros, from the University of Taubaté, a city in inner-state São Paulo, created an indicator to calculate mothers’ exposure to air pollutants. Shortly after this, they sought out information about 631 children born at hospitals from 14 different districts in the southern part of the city of São Paulo, from August 2000 to January 2001.
Andréa and Gouveia found signs of smoke in the stories of 318 babies who died during their first week of life. Obviously, pollution was not the direct cause of death. But it had somehow contributed. Once other factors that increase the death risk during this period, such as low weight at birth, the mother’s age and failure to carry out prenatal tests were discounted, what emerged was the impact of pollution: the babies of women who had inhaled more gases and smoke during pregnancy had a 50% greater risk of dying in the first days after birth. “There are factors that are more important regarding the death of newborns, but this figure indicates that air pollutants have a significant negative effect on the health of pregnant women and their children,” states Gouveia.
Nor was heavy traffic needed for the effect to appear. Babies of women who lived in an area within a few blocks from streets with 6 to 45 vehicles an hour during peak periods – in other words, very peaceful areas – showed a 46% greater risk of dying during their first week of life, according to an article shortly to be published in the journal Environmental Health Perspectives.
This is not the first time that pollution has been linked to perinatal mortality, which covers the pregnancy period plus the first week after birth. Years ago, Dr. Paulo Hilário Saldiva’s team, also from USP, who for almost two decades had been studying the effects of pollution on health, showed that the most polluted days in the São Paulo state capital were also those with the greatest number of miscarriages. Saldiva, together with Dr. Luiz Amateur Pereira, also found that carbon monoxide (CO) was the pollutant linked to the highest probability of death of the fetuses. Co is a colorless, odorless gas that results from the incomplete burning of automobile fuels, as they explained in 1998 in the journal Environmental Health Perspectives.
The work of Andréa and Gouveia leaves us with a warning and doubts; after all, what changes does pollution cause in the body to increase the risk of infant death? “We still don’t have a precise understanding of the biological mechanism that is behind this effect,” comments Gouveia, who recently declared that pollution accounts for 5% of deaths due to respiratory problems among children and the elderly in seven state capitals (São Paulo, Rio de Janeiro, Belo Horizonte, Vitória, Curitiba, Fortaleza and Porto Alegre).
The answer to this question seems to come from the floor immediately below Gouveia’s office at USP’s Medical School. In the Experimental Atmospheric Pollution Laboratory, the team coordinated by Saldiva and the pathologist Thais Mauad recently completed a battery of tests in which they compared the impact on people’s health of living in polluted environments such as the streets of São Paulo versus living in a place with pure, clean air.
Laboratory in the garden
One important discovery is that pollution alters the structure of the placenta, the organ responsible for transporting oxygen and nutrients to the fetus. Over a number of months, Thais, Saldiva and biologist Mariana Matera kept several generations of mice in two types of environment with controlled air quality – a polluted one and an unpolluted one. It would be virtually impossible to do this with human beings.
In the gardens of the Medical School, just 20 meters from the corner of Dr. Arnaldo avenue with Teodoro Sampaio Street, an intersection with heavy traffic throughout most of the day, they installed two chambers with cages containing mice. One chamber received the polluted air from the streets, the same that is breathed in by those who circulate in the area around the Clinicas Hospital, while the other received filtered air.
In each chamber the researchers maintained identical groups of rodents in various phases of the reproductive cycle: prior to conception, during gestation and after the birth of their issue. To isolate the effects on males from those experienced by the females, Saldiva and Mariana repeated the experiment, putting males that had been raised in the pure air environment together with females from the polluted environment – and vice-versa.
At the end of each gestation, Mariana evaluated the structure of the placenta and the weight of the brood. In the case of the placenta of the female mice created in the polluted environment, the channels that carry the maternal blood to the embryo were narrower. And the tissue through which the exchange of oxygen and nutrients takes place was finer. In an article in the September issue of the journal Biology of Reproduction, the researchers describe how the capillaries of the fetus, which are responsible for the absorption of food and oxygen, were spread over a larger surface, probably as a reaction to the difficulty in obtaining nutrients. “It is an indication that the placenta is making a huge effort to adapt in order to overcome this adverse situation,” explains Mariana.
Even so, the brood of the females that breathed polluted air were smaller and weighed less than those of the females given clean air – the loss in weight was greater in the case of the brood of the female mice that were exposed to pollution both before and during gestation. “It did not matter how long the exposure to the pollutants lasted. The result was always the same: a brood with low weight, which increases the risk of developing diabetes and cardiovascular problems in adult life,” explains Mariana. “The alterations in the placenta indicate that there was even an increase in the amount of oxygen transported, but the transfer of nutrients may be compromised”.
The damages, however, began at a much earlier stage of the reproductive cycle. The female rodents that lived in the polluted environment were less fertile – they produced 36% fewer cells capable of germination – and showed a greater frequency of miscarriage than those that lived in the chamber containing filtered air, according to the article in Environmental Research. Somewhat surprisingly, the fertile period of the females that grew up breathing polluted air lasted, on average, three times longer than that of their counterparts that were brought up in a pure air environment. Even this physiological alteration did not favor reproduction. Although they remained fertile for a longer period, they took longer than normal to accept male sexual advances, explains the biologist.
The tests also produced experimental evidence on how prolonged exposure to pollutants – especially to finer particles, with a diameter of less than 2.5 micrometers – harms lung development. On the 15th and 90th days after birth, Thais evaluated the structure and capacity of the lungs of four groups of newborn mice that were the offspring of parents that had spent their lives either in the polluted atmosphere or in the clean air chamber – these periods equate, respectively, to childhood and the start of adult life in human beings.
A tennis court in your chest
The mice offspring that had grown up in the polluted atmosphere and whose parents had also breathed air loaded with pollutant particles throughout their entire lives had less developed lungs and a smaller respiratory capacity than the animals that were only exposed to pollution either within the womb or after birth. Not surprisingly, the rodents that had always been given pure air and whose parents had also breathed filtered air produced the best performance. “We don’t yet know whether the damage observed in the rodents is definitive,” points out Thais.
If these results, which were presented in October of last year in the American Journal of Respiratory and Critical Care Medicine, could be transposed to human beings, it would be the equivalent of saying that people from the city of São Paulo, whose parents were also born and bred in the same city, in addition to – and also on account of the fact – that they live in a city with a quality of air that is far short of what is desirable, would have a higher risk of lower respiratory capacity.
Most of the damage occurred during the formation of the alveoli, the microscopic sacs in which the gaseous exchanges of respiration take place – the oxygen contained in the inhaled air is taken up by the blood and the carbon dioxide is eliminated into the atmosphere. What happens during this phase can be decisive for adults’ respiratory capacity. The period between childhood and the end of puberty sees the formation of 85% of the 300 million alveoli in human lungs, which add up to an area equal to the size of a tennis court for the exchange of gases.
Since they are very fine, particles with a diameter of less than 2.5 micrometers are not retained by the microscopic hairs that line the breathing passages and that filter the inhaled air. When these polluting particles reach the alveoli, they damage them and alter their development, explains Thais. Fewer alveoli mean that there is a smaller surface for the exchange of gases.
Everyone knows the solution to reduce the effects of pollution and improve the quality of people’s lives – also reducing public expenditure with patient admissions and treatments (see Pesquisa FAPESP 129): to expand the public transport network and improve its quality; to reduce automobile usage; to oversee the emission of pollutants; to modernize the bus and truck fleets; and to improve the quality of the fuel sold in Brazil. “As with any environmental issue, these measures demand that the authorities take action, and that society also plays a role,” says Gouveia. “We, the citizens, cannot fail to play our part in this story.”
The impact of exposure to atmospheric pollutants inside the womb and during the early stages of post-natal development on the development of adverse changes in adult life (nº 03/10772-9); Type: Thematic Project; Coordinator: Paulo Hilário Saldiva – FMUSP; Investment: R$ 528,826.84 (FAPESP)
MEDEIROS, A.P.P. et al. Traffic-related air pollution and perinatal mortality: a case-control study. Environmental Health Perspectives, v. 116, no.12, Dec. 2008.
VERAS, M. M. et al. Particulate urban air pollution affects the functional morphology of mouse placenta. Biology of Reproduction, v. 79, p. 578-584, Sep. 2008.
MAUAD, T. et al. Chronic exposure to ambient levels of urban particles affects mouse lung development. American Journal of Respiratory and Critical Care Medicine, v.178, p. 721-728, Oct. 2008.