Weather events and respiratory diseases in children: case studies in the metropolitan region of São Paulo, Brazil

This paper presents a preliminary analysis of meteorological variables and their relationship with respiratory morbidity in children under two years old of São Paulo city, taking into account the synoptical systems and their constructive structures of residences. Measurements of indoor air temperature and relative humidity were collected using a thermohygrographic across of 378 residences, between years 2003 to 2006. Outdoor meteorological variables have been obtained from meteorological station. A summary with four case studies is shown relating the thermal behavior in each residence and the onset of respiratory illness in children (wheezing). The results show associations of children respiratory crises and air temperature fall and increase of relative humidity, associated with maritime polar air masses and frontal systems (cold front). Specific residences have higher indoor humidity values than others, due to their constructive types and it is an important factor to bring out wheezing problems. Considering such results, acknowledging periods favorable to occurrences of wheezing in children, as well as the constructive type of residences, it is feasible to predict respiratory morbidity and to establish public policy in order to alert the population, minimizing weather/climate impacts on children's health


INTRODUCTION
Since the earliest days of human history, the interest, necessity, or curiosity of understanding the relationship between the different weather conditions and human body's physiological response to these changes has always existed. Hippocrates, in his book "Air, Waters and Places", dated about 400 BC, described qualitatively the main variables that significantly affect thermal comfort: temperature, winds, relative humidity, and radiation; (Monteiro & Alucci, 2005). In the seventeenth century, the first measurements of air temperature were held in Florence and Beijing, however, if they the goal was to seek views on thermal sensations of certain environments, those were considered vague. In the early nineteenth century there were some preliminary studies investigating the influence of thermal stress in the textile industry workers who had health problems.
The air in the indoor environment is an exposure that dominates human beings. Since human beings spend approximately 90% of their lives indoors and more than half of the air breathed (about 90%) in a lifetime is inhaled in domestic environments, a good understanding of thermal conditions found within such environments is naturally necessary and very important. In that sense, many studies have been made taking into account not only the physical variables of the environment, but the characteristics of buildings and behavior of their occupants. The research has assessed thermal performance of buildings (homes) and their living conditions (Viamont, 1996;Givoni 1992 and1999;Vechia 2005;Vecchia and Givonni, 2001;Papst and Lamberts, 2001;Cardoso, 2007;Nedel, 2008).
Studies on exposure to indoor environmental risk factors and their effects on health in developed countries have mainly been conducted in northern Europe and North America. Emenius et al. (2004) found that living in relatively new apartment buildings, in singlefamily homes with crawl space/concrete slab foundation, with elevated indoor humidity, and report wintertime windowpane condensation were associated with current wheezing in infants. Thus, according to these authors, improvements in the building quality may have potential to prevent infant wheezing. According to Sundell (1999), there is strong evidence of associations between indoor air quality and lung cancer, allergies and respiratory infections. Regarding indoor ventilation, Smith (2003), analyzing the condensation on glass windows, reported that inadequate ventilation was the main risk factor for the onset of coughing, asthma, and respiratory infection and a significant increase in allergies among residents.
Respiratory diseases, especially in childhood represent a major public health problem.
The causes of these diseases can be infectious (virus and bacteria), such as colds and pneumonia, or non-infectious as asthma and bronchitis (Cardoso, 2007). Some children have wheezing as a manifestation of these respiratory diseases, sometimes accompanied by fatigue or shortness of breath. Cardoso also comments that the hiss is a type of most common manifestation in children of mothers with asthma or a history of allergy (allergic rhinitis, for example). Among the various factors for the increased number of respiratory diseases and severity of hospitalizations, environmental factors play a role of utmost importance. Sudden changes of time, for example, helps degrading the quality of breathing air, especially when the site is under the influence of cold and dry air masses, which makes the dispersion of pollutants in the atmosphere. Furthermore, the authors investigating the residences´ microclimate which was observed contribution for respiratory problems related to indoor conditions due to their deficient constructive characteristics. The high temperature ranges were observed and they were related to children wheezing.
Considering the above described, it becomes factual the importance of knowing the temperatures in home environments, not only regarding thermal comfort, but especially because of the fact that bad adequacy of local microclimate might affect health, especially among children. This paper is a preliminary view which aims to assess the meteorological conditions favorable to the occurrence of respiratory disease (wheezing) in children below two years old in the city of Sao Paulo, Brazil, as well as the role of homes for these illnesses. The hypothesis to be investigated is that the household, through their constructive kinds, can play an important role at the beginning of the wheezing in children, especially, with regard to meteorological variables: air temperature and relative humidity.

a) Study area
The area of this study is the Metropolitan Region of Sao Paulo (MRSP), located in the southeast portion of Brazil, which has a population of approximately 17,000,000 inhabitants and at currently with over 7,000,000 vehicles. and 2005, respectively. The relative humidity varies between 20% and 100%. Due to its proximity to the Atlantic Ocean (120 km away to the south) the region is influenced by the effect of sea breeze that is a constant in the local weather. The average annual precipitation is 1,317 mm (IAG/USP station) and can be divided into two main seasons: a rainy season which includes the period from October to April and a dry season that goes from May to September. Another factor of great importance to the health of the population is the high concentration of air pollutants observed in the city. Coming mainly from anthropogenic mobile sources pollutants such as PM10, NOx, SO2, O3, CO are the most commonly measured and the most worrying. Among the regulated pollutants that have their environmental concentrations increased during the winter, and eventually exceed the standards of air quality, there are inhalable particles (PM10), carbon monoxide (CO) and nitrogen dioxide (NO2). Moreover, in despite of being less favorable to the formation of ozone, exceeding the standards of air quality in this period is a frequent occurrence.
Throughout the winter, such exceeding levels in the city of Sao Paulo are favored by the condition of thermal inversion -when a temperature inversion occurs, increasing with height and imprisoning the pollutants in the lower layers of the atmosphere -something constant in this season. In a simplified way, inhalable particles are those with aerodynamic diameter less than 10 μm, enabling these particles to penetrate the respiratory tract. Studies by the CETESB (Companhia de Tecnologia de Saneamento Ambiental -Brazilian version of EPA in the USA) in the MRSP show that about 40% of these particles are emitted by motor vehicles (mainly by diesel vehicles). Another source considered important is the dust of the streets, equivalent to about 25% of the pollutant concentration. Among the inhalable particles, there are inhalable thin particles, with a diameter less than 2.5 μm, for which there is no national legal concentration threshold, but which nevertheless are very important in terms of health, since they penetrate more deeply into the respiratory tract (Cançado et al, 2006 Table 1 presents the distribution of households with their child's identification, date of consultation, date of the beginning of the problem, as well as the respiratory complication. In order to assess the constructive types of buildings, it was used the classification proposed by Cardoso, 2007 (by cover/roof, ceiling and wall) which has characterized the dwellings in twelve different constructive types (Table 2).

RESULTS AND DISCUSSION
In order to analyze the impact of dwelling types in the onset of wheezing problems in children, a correlation analysis of data was performed organized. Analyzing with more detail the role played by the residences constructive type (groups) in the onset of wheezing in children, particular case studies were conducted. The purpose is to show that high (low) amount of inside moisture has influence to faster (slower) beginning of respiratory problem. Different residences are compared, located in diverse places of the city, sampled on the same periods (in order to compare indoor moisture in the residences).
The events are shown as it follows: from Case Study I to IV.    house, it was necessary that these moisture levels were kept higher.
Summarizing, this case study shows that a cold front could influences the residences of São Paulo city moisture levels in both children from both households 1025 and 1027.
However, the child living in household 1025 presented the respiratory problem (wheezing) only for a few hours (one day; 02/05) after the beginning of the increase in humidity and rainfall, while the residence 1027 child presented the noisy breathing problems only 3 days later (05/05). The constructive characteristics of residences can be responsible for this difference. RHrmín), and colder and "slightly" more humid during the night (morning) (smaller Tmín and larger RHmax), which can be explained by the constructions, with coverage of low thermal inertia (tile cement) that provides a greater accumulation of heat during the day (the incidence of solar radiation) and a rapid cooling at night with large spaces between their structures allowing the entry of large volumes of air (as earlier mentioned). The 1027 residence is characterized by having a greater amount of moisture (RHmin), mainly during the whole day. When the mean RH is observed, it is correct to say that, in average, this house is wetter than house 1025.
By characterizing the periods of measurements by seasons; summer, fall and winter, it is clear that in the summer and in the winter seasons these differences (T and RH) between the houses are more evident (in the Autumn, this difference is hardly noticeable). The 1025 house is the most uncomfortable for both seasons, being colder in winter and hotter in summer. Comparing two households with the outside environment (IAG/USP meteorological station, figure 1b), is observed in general that both are warmer and wetter than the outside environment (not shown here).  Source: the authors Analyzing the constructive characteristics of these households it is observed that both 1008 and 1027 are composed of walls with bricks, lack of lining and cover slab. These construction types store a large amount of moisture inside, and its type of coverage (concrete slab) and being under and on other floors (between floors) prevents the ideal (and equal) receipt of solar radiation in its total structure. In addition, the ventilation rate in such constructive characteristics seems to be poor (with very small areas or without windows, as the case of the house 1008). In the episodes of wheezing of the children 1027

ii) Case Study II: Events
and 1008 (09/14 and 09/15/2003, respectively), the city of São Paulo was under the influence of a cold air mass (CAM), which associated with the anticyclone positioned on the Atlantic Ocean continued the moisture flows and affect decrease of temperatures (as described in Figure 3).   (Tmin), maximum (Tmax) and mean (Tmean) temperature (°C), and minimum (RHmín), maximum (RHmáx) and mean (RHmean) relative humidity (%) observed at houses 1027 and 1008, and its corresponding season (S): summer (S), fall (F), winter (W).  minimize the effects of the external environmental. An increase/decrease in external of T and RH, for instance, can impact quickly and begin onset of respiratory illnesses (wheezing) in children on the same day of decrease of outside temperatures -or after a few hours ("lag" 0 day). Any increase or decrease in T and RH in the external environment (even small) could change the conditions of the indoor environment. In the case of the wheezing episode presented by children in 1196 house, it was noticed that the problem appeared on the same day of the arrival of the frontal system (at night, December, 06 th ), which increased air humidity, producing rainfalls and drop in temperatures (Figure 4b). that the contribution to the more stored of high humidity inside of the house (1133), and this can be directly associated with the onset respiratory complications in the child on subsequent days (noisy breathing; December, 09 th ). Table 6 shows the internal variables T and RH in houses measured in 1196 and 1133 residences. Residence 1196 (measured on the third coldest weeks of winter, 2004) is warmer and wetter when compared to the outside environment (larger Tmed and RHméd). This moisture is considerably higher during the day (RHmín: 71.5% and 39%, respectively). Throughout the night, the indoor humidity is also high, but slightly higher than the external environment (RHmáx: 98% and 95%, respectively). Considering only the temperature effects, it was observed maximum values very close between indoor and outdoor environment, and the minimum values higher (inside) than the ones measured outside (meteorological station). Regarding house 1133, it was also characterized as warmer as and wetter than outside environment, especially during the afternoons (when the RHmin was higher: 70% and 52%, respectively). However, the maximum temperature was smaller than outside temperatures (this might be an indication that there was no good sunlight in the house This suggests that the households have an important role in the onset of respiratory problems in children. Table 6 -Values of minimum (Tmin). maximum (Tmax) and mean (Tmean) temperature (°C). and minimum (RHmín). maximum (RHmáx) and mean (RHmean) relative humidity (%) observed at houses 1196 and 1133.

iv) Case Study IV: Events of 15/09/2004 and 17/09/2004
Through Figure  On the other hand, house 1108 (similar to house 1133, already discussed in this research), consisting of walls with hollow bricks, unlined, slab cover, and tile floor. Thus, it has a greater thermal insulation (roof slab) when compared to 1196 (title asbestos cement roof). Table 7 shows the indoor T and RH variables for households 1108 and 1196, and the periods of measurements. Analyzing the temperatures between houses, it is observed that in average both maximum and minimum values are noticeable very close, however, the difference between maximum and minimum is slightly larger in 1108. The first statement is maybe an indicative of a low (or nothing) sunshine incidence over both houses, particularly in house 1196, which also close to other neighboring houses and increasing the amount of shaded areas in this housing. Such hypothesis is supported by the fact that if there is incidence of sunlight in these residences, the 1196 house, due to the constructive type would present higher temperatures than 1108 house. In the outside environment, these days were sunny with low relative humidity, light winds, and cloudless.

CONCLUSIONS
The analysis of association between respiratory diseases (wheezing and noisy breathing) in children in the city of Sao Paulo and meteorological conditions, across these case studies, suggests the strong contribution of household constructive types in children, since the weather conditions changes seem to be modulating respiratory problems. Residences of lower thermal mass are the most harmful. In addition, meteorological events as cold fronts and cold air masses provide high amount of moisture inside environments, which are also highly prejudicial to children's health.
Among children who presented major problems (wheezing) live in buildings with high moisture content indoor (mainly) and lower thermal insulation (table 3). Observing other respiratory problems related to wheezing as noisy breathing and cough (not shown here) it was possible to notice, in general, that the residences also present these constructive types. However, of the days for the beginning of the problem are different for each child.
In residences with less thermal insulation (1025 and 1196 houses) the children had, in general, the problem on the same day ("lag" of ~0.7 days, or few hours later) of drop in outdoor air temperature (meteorological station). On the other hand, children living in homes with better heat insulation and, consequently, with more moisture content inside the residence (1008, 1027, 1133 houses) present the beginning of wheezing complications two days later of decrease external air temperature ("lag" of ~2 days). These differences can be attributed to higher (lower) gain (loss) of heat through the roof, beyond the intrinsic biological conditions of each child (who were not evaluated in this study). It is also extremely useful to emphasize the role played by the areas of shading caused by the poor location of households (close to neighboring houses; 1196 and 1008 houses) which can accelerate the onset of respiratory problems in children, being an important factor in determining this disease. One important application of this study is not introducing more moisture environments (residences) of the city of Sao Paulo during low air humidity episodes (winter season, mainly). It is extremely unwise and dangerous, because it only could result in high indoor thermal discomfort and the beginning of allergic complications, such as fungi and mites damaging health, especially in children. We also encourage other studies to investigative the characteristics of each household (location, household habits, presence of fungi in walls, household crowding, smoking persons in family, maternal education, family genetics, etc ...), in addition, to each biological child.
The findings showed in this paper are preliminary.