The quality of air inside buildings is a problem almost unknown in Brazil, according to professor Racine Prado, of the Polytechnic School of the University of São Paulo (USP), author of research financed by FAPESP in order to detect pollutants in buildings in the city of São Paulo.
Racine, who had the assistance of the scholarship winner Adriano Trotta do Carmo, based his work on tolerance levels according to American and Canadian standards. The work revealed the importance of ventilation in order to disperse pollutants and showed that their concentration can depend a lot on the size of the internal areas, and on the number of occupants.
Racine explains that in cities a large proportion of the people spend between 80% and 90% of their time in buildings, many of them considered to be “ill” due to the existence of polluting sources within them or in their vicinity and to poor ventilation. Today, in order to save energy, little use is made of natural ventilation through open windows as, after the oil crisis of the 70s, the “buildings with few openings for ventilation that spend less energy to maintain air conditioning and air circulation” became widespread. Buildings have become more and more closed up and endowed with controls for ventilation, temperature and humidity, while air quality was ignored. Thus, “the average concentrations of various pollutants in indoor air have increased considerably, due to the infrequent changes of air between the exterior and the interior of the building.” Various gases – carbon monoxide and carbon dioxide, ammonia, sulfur oxides and nitrogen oxides – are spawned by construction materials, mustiness cleaning, from the kitchen, the washing/drying of clothes and human metabolism itself.
This has caused two pathologies. One is the “syndrome of the sick building”, a transitory state on the part of the users (close to 20%), whose symptoms – headache, nausea, irritation of the eyes, nose and throat, tiredness, lack of concentration and skin problems – normally disappear when the person leaves the building. The other is the “illness related to the building”, caused by bacteria, viruses and fungi.
The most exposed
Professor Racine highlighted the pollutants ammonia, carbon monoxide, carbon dioxide, nitrogen dioxide, sulfur dioxide and formaldehyde. He picked out buildings that were most exposed to them, via characteristics such as an exterior with few openings, probability of a high internal heat generation or large movement of people and cars. He chose hospitals, malls, car repair shops, commercial buildings and universities. Of the 23 chosen, 12 allowed him to take measurements: 2 hospitals, 1 car repair shop, 5 commercial buildings and 4 USP campuses. Professor Racine used a portable gas measuring machine linked to a microprocessor.
The choice also considered the probable type of pollutant. For example, in a university classroom the breathing of the students produces carbon dioxide (CO2), a relatively non-toxic gas, but considered to be a good indicator of air quality. In the room researched there were 1,000 ppm (parts per million) of CO2, a level higher than the one which can give people the feeling of stuffiness and that indicates insufficient ventilation to dilute more noxious pollutants.
In the car repair shop, to the CO2 was added a toxic gas, carbon monoxide (CO), a product from the combustion of fossil fuel above all from cars, and whose safety limit is 50 ppm. The car repair shop, a shed of 2,400 m2 with a front entrance of 6 meters, frontal windows and five circulation fans on the roof, revealed average levels of CO that went from 173 ppm next to the well ventilated entrance, to 500 ppm in the area of the body shop and paint shop in the rear – an excess that caused respiratory problems.
The hospitals were polluted: instruments sterilization, as well as the large number of people and of microorganisms contribute to this. In one of them, the level of CO was of 148 ppm in the waiting room and in the area of endoscope, much more than in the machinery room (52 ppm), full of polluting equipment but with an efficient exhaust system. In another hospital, the highest level of CO was lower in the garage (98 ppm) than at reception (110 ppm) and in the snack bar (125 ppm). In the restaurant, the burning of liquefied petroleum gas in the kitchen released at the limit of tolerance both carbon monoxide (average of 55 ppm) and carbon dioxide (1,000 ppm).
Other dangerous gases found were ammonia, sulfur dioxide and formaldehyde. Present in urine, ammonia (NH3) has a suffocating smell and tolerance levels of from 25 to 50 ppm. Sulfur dioxide (SO2), another by-product of combustion fuel, also has a suffocating smell and above 6 ppm already begins to irritate the respiratory system. Formaldehyde, produced from cleaning and construction materials, irritates the mucous and has a maximum index of 0.4 ppm in internal environments and 1.0 ppm in industry.
The basic conclusion to the study was that the excessive quantity of people in a determined area, favors the concentration of pollutants much more than it had been expected – even more than the presence of polluting sources such as certain pieces of equipment and floor cleaning/polishing fluids. The level of CO increases considerably where there is combustion, above all generated by cars. However, the presence of CO in an office, although still at an acceptable level, suggests that this gas – not produced by people – had been introduced via the air conditioning system.
Data obtained in a commercial building under distinct conditions (closed and open environments) showed that computers, printers and carpets exhale, as well as ammonia, nitrogen dioxide (NO2) – a gas when concentrated of dark brown color and with a pungent smell, produced above all by vehicle traffic, which irritates eyes, throat and the respiratory system, The maximum recommended level is 5 ppm in industrial environments. Anyhow, the study points out, it would be possible to control the polluting sources or at least increase air circulation, which would then disperse the pollutants.
The objective was to provide basic data about internal air quality to graduating students, to define the pollutants, their most common sources and the effects on health, as well as to give a general vision of how to prevent and solve the problem. In Brazil, almost no research has been done in this area, but there are lots of sick buildings, beginning with some in the Federal capital, as it made the news recently. The study, that could be the foundation for more comprehensive studies, comes up with procedures that can minimize the problem.
• Professor Racine Tadeu Araújo Prado, 45 years of age, graduated as a civil engineer from the Polytechnic School of USP (1987), where he took his masters (1991) and doctorate (1996). He has specialized in building systems.
Project: Investigation into the Field of Pollutants in the Internal Air of Buildings
Investment: R$ 20,348.75