A systematic review of the physical and chemical characteristics of pollutants from biomass burning and combustion of fossil fuels and health effects in Brazil

The aim of this study was to carry out a review of scientific literature published in Brazil between 2000 and 2009 on the characteristics of air pollutants from different emission sources, especially particulate matter (PM) and its effects on respiratory health. Using electronic databases, a systematic literature review was performed of all research related to air pollutant emissions. Publications were analyzed to identify the physical and chemical characteristics of pollutants from different emission sources and their related effects on the respiratory system. The PM2.5 is composed predominantly of organic compounds with 20% of inorganic elements. Higher concentrations of metals were detected in metropolitan areas than in biomass burning regions. The relative risk of hospital admissions due to respiratory diseases in children was higher than in the elderly population. The results of studies of health effects of air pollution are specific to the region where the emissions occurred and should not be used to depict the situation in other areas with different emission sources. Environmental Pollutants; Air Pollutants; Particulate Matter; Respiratory Tract Diseases Introduction Exposure to air pollutants has been shown by several epidemiological and toxicological studies to have noxious effects on human health 1,2,3. Environmental exposure to particulate matter (PM) has been widely studied because of its physical characteristics and multi-elemental composition which varies depending on the emission source 4,5. The main sources of PM emissions are fossil fuel combustion and biomass burning 6,7. Globally, Brazil makes a significant contribution to PM emissions because some regions of the country have extremely high levels of air pollution. In the South and Southeast Regions, the development of automobiles and industry are the main cause of these high levels 8, whereas in the southern and eastern Brazilian Amazon the expansion of agribusiness and forest fires are the main contributors to PM emissions, especially in the region known as the “Arc of Deforestation” 9. Aerosol particles in the atmosphere influence the Earth’s radiation balance and climate, atmospheric chemistry, visibility and human health on a local to global scale. The transport and deposition chemistry of these particles and their effects on solar radiation and human health depend largely on their size, distribution, composition, morphology and surface area 10. These characteristics are important, especially in the Brazilian Amazon region where forest burning is 1678 REVISÃO REVIEW PHYSICAL AND CHEMICAL CHARACTERISTICS OF POLLUTANTS AND EFFECTS ON HEALTH 1679 Cad. Saúde Pública, Rio de Janeiro, 27(9):1678-1698, set, 2011 widespread during the dry season. Studies show that individuals living in exposed areas located far from the source can demonstrate the same adverse respiratory effects as those experienced by individuals at the source itself 11. At the height of the dry season, between July and October, the Brazilian Amazon Region is responsible for approximately 70% of biomass burning in Brazil (Instituto Brasileiro do Meio Ambiente. http://www.ibama.gov.br/prevfogo/ areas-tematicas/monitoramento/dados-de-fo cos-de-calor, accessed on 10/Mar/2010) leading to significant damage to the savanna and Amazon Forest. On average, forest fires in the Brazilian Amazon are responsible for 67% of PM2.5 emissions 12,13. In other regions of Brazil, most fires are a result of sugarcane plantation burning 14. However, in metropolitan areas of Brazil the primary cause of PM emissions are motor vehicles 15. The health effects of atmospheric particles are influenced by particle size (aerodynamic diameter). The diameter of atmospheric particles ranges from 1nm to 100μm. PM10 and PM2.5 particles have an aerodynamic diameter of less than 10μm and 2.5μm, respectively. Ultrafine particles, or PM0.1 particles, have a thermodynamic diameter of less than 0.1μm. PM2.5 particle fractions are called “fine particles” and those particles with a diameter of between 10μm and 2.5μm are called “coarse particles” 3,4. The concentration, size, chemical composition and toxicological characteristics of pollutants, including PM, are determined by the emission source 4,16. This study aims to present an overview of the scientific literature on the characteristics of air pollutants, especially particulate matter and their respiratory health effects, from the different types of sources of pollutant emissions in Brazil published between 2000 and 2009. Materials and methods


Introduction
Exposure to air pollutants has been shown by several epidemiological and toxicological studies to have noxious effects on human health 1,2,3 .Environmental exposure to particulate matter (PM) has been widely studied because of its physical characteristics and multi-elemental composition which varies depending on the emission source 4,5 .
The main sources of PM emissions are fossil fuel combustion and biomass burning 6,7 .Globally, Brazil makes a significant contribution to PM emissions because some regions of the country have extremely high levels of air pollution.In the South and Southeast Regions, the development of automobiles and industry are the main cause of these high levels 8 , whereas in the southern and eastern Brazilian Amazon the expansion of agribusiness and forest fires are the main contributors to PM emissions, especially in the region known as the "Arc of Deforestation" 9 .
Aerosol particles in the atmosphere influence the Earth's radiation balance and climate, atmospheric chemistry, visibility and human health on a local to global scale.The transport and deposition chemistry of these particles and their effects on solar radiation and human health depend largely on their size, distribution, composition, morphology and surface area 10 .These characteristics are important, especially in the Brazilian Amazon region where forest burning is Cad.Saúde Pública, Rio de Janeiro, 27 (9):1678-1698, set, 2011 widespread during the dry season.Studies show that individuals living in exposed areas located far from the source can demonstrate the same adverse respiratory effects as those experienced by individuals at the source itself 11 .
At the height of the dry season, between July and October, the Brazilian Amazon Region is responsible for approximately 70% of biomass burning in Brazil (Instituto Brasileiro do Meio Ambiente.http://www.ibama.gov.br/prevfogo/areas-tematicas/monitoramento/dados-de-fo cos-de-calor, accessed on 10/Mar/2010) leading to significant damage to the savanna and Amazon Forest.On average, forest fires in the Brazilian Amazon are responsible for 67% of PM 2.5 emissions 12,13 .In other regions of Brazil, most fires are a result of sugarcane plantation burning 14 .However, in metropolitan areas of Brazil the primary cause of PM emissions are motor vehicles 15 .
The health effects of atmospheric particles are influenced by particle size (aerodynamic diameter).The diameter of atmospheric particles ranges from 1nm to 100µm.PM 10 and PM 2.5 particles have an aerodynamic diameter of less than 10µm and 2.5µm, respectively.Ultrafine particles, or PM 0.1 particles, have a thermodynamic diameter of less than 0.1µm.PM 2.5 particle fractions are called "fine particles" and those particles with a diameter of between 10µm and 2.5µm are called "coarse particles" 3,4 .
The concentration, size, chemical composition and toxicological characteristics of pollutants, including PM, are determined by the emission source 4,16 .This study aims to present an overview of the scientific literature on the characteristics of air pollutants, especially particulate matter and their respiratory health effects, from the different types of sources of pollutant emissions in Brazil published between 2000 and 2009.

Study design
A systematic literature review of all research related to vehicular, industrial and biomass burning pollutant emissions published between 2000 and 2009 was performed using electronic databases.Reviews of earlier studies were also conducted 14,17,18,19,20 .Priority was given to publications on the physical and chemical characteristics of particulate matter from the different types of emission sources followed by studies related to respiratory system effects.The following criteria were used to select and analyze studies regarding the effects of PM on the respiratory system: study area, year of publication, source characteristics, susceptible group and health outcomes.Reviews and studies that did not show the outcome of respiratory diseases were excluded.Articles on the physical and chemical characteristics of PM were then reviewed using the following criteria: source characteristics, study area, year in which the data was collected, particle concentration and chemical composition.Only those studies that included information on particle size, concentration and elemental composition of aerosols were included.
To compare the respiratory effects of exposure to PM and the relative risk (RR) of mortality and hospitalization in children and the elderly, increments of 10µg/m 3 in PM 10 levels were used.RR was recalculated for those articles that did not show a variation in concentrations of 10µg/m 3 , and the standard error and coefficient (β) were calculated for mortality and hospitalization related to variations in PM 10 concentrations.Gouveia & Fletcher 21,22 and Braga et al. 23 calculated the standard error and β using RR and confidence interval (CI).This review only included the results of articles where RR and CI figures were described in tables or the text.
Reports, texts, inventories and guides produced by the Large Scale Biosphere-Atmosphere Experiment in Amazonia (LBA; http://lba.inpa.gov.br/lba/), the World Health Organization (WHO; http://www.who.int/topics/air_pollution/en/), the Environment Protection Agency (EPA; http://www.epa.gov/air/airpollutants.ht ml) and the National Institute for Space Research (INPE; http://sigma.cptec.inpe.br/queimadas/)were used as information sources for the discussion of the literature.Articles published in 2010 and which were not indexed during the search period were included in the discussion of results.
Approximately 20 publications dealt with the physical and chemical characteristics of vehicular, industrial and biomass burning pollutant emissions.The number of studies conducted in biomass burning areas was greater than the number conducted in metropolitan areas for all years apart from 2004, 2008 and 2009.The largest numbers of articles on fires were published in 2005, with 5 publications, whereas the largest numbers of articles on industrial sources and motor vehicles were published in 2008.
Most of the articles reviewed on health effects arising from exposure to particles derived from industry and motor vehicles in metropolitan areas were published in 2009.With respect to biomass burning, a total of 13 articles were published between 2000 and 2009.

Physical and chemical characteristics of pollutants derived from biomass burning
A summary of the articles concerning the main physical and chemical characteristics of pollutants derived from biomass burning is presented in Table 1.The Amazon biome was the most studied area in articles on the physical and chemical characteristics of PM 77,82 .Studies in this region show that PM 10 and PM 2.5 were predominantly composed of organic compounds 75,78,81,86 , and in the case of PM 2.5 these substances made up 70% to 92% of its composition 75 .Among the organic elements, Black Carbon (BC) made up between 5% and 15% of PM 2.5 , with values ranging from 5.5µg/m 3 to 16µg/m 3 during peak burning 76,77 .During the dry season in the Southeast Region of Brazil, BC levels from burning sugarcane were lower than those measured in the Brazilian Amazon 52,84 .
In the Amazon biome, high concentrations of biogenic elements were identified for PM 10 dur-ing the rainy season 87 .During the dry season, PM 2.5 is predominantly composed of BC, sulphates (SO 4 2-), nitrates (NO 3 ) and metals 12,77,87 .Yamasoe et al. 75 investigated the chemical composition of PM 2.5 relating to the burning phases or stages and detected that potassium (K), chlorine (Cl) and sulphate (SO 4 2-) were the dominant chemical elements.Ammonia (NH 3 ) was also found in fractions of PM 2.5 during the dry season in the Brazilian Amazon 77,81 .These same characteristics were observed in the Southeast Region of Brazil in areas of sugarcane burning 52,80,84 .
In biomass burning areas in the Southeast Region of Brazil and Brazilian Amazon region, studies identified concentrations of metals such as zinc (Zn), iron (Fe), lead (Pb), copper (Cu) and mercury (Hg) in the elemental composition of PM 2.5 .It is probable that mining activities are responsible for the concentrations of Hg 12,75,76 .
In the Brazilian Amazon, concentrations of PM 10 and PM 2.5 were higher during the dry season, reaching peaks of 600µg/m 3 and 350µg/m 3 respectively 77 , It should be noted however that this information comes from an article that referred to data collected in the 1990s.Sugarcane burning areas showed average PM 2.5 levels ranging from 9.3µg/m 3 to 238µg/m 3 (σ 14.5µg/m 3 ) 84 .Currently, the Amazon biome shows peak PM 2.5 concentrations of between 225µg/m 3 (between September and November 2002) 85 and 450µg/ m 3 (September 2005) 65 , whereas the Southeast Region, in areas of sugarcane burning, mean levels of Total Suspended Particles (TSP) of 47µg/m 3 with a standard deviation of 26.4µg/m 3 and peak value of 138µg/m 3 were identified between 2003 and 2004 58 .

Physical and chemical characteristics of pollutants from industrial activities and motor vehicles
The physical and chemical characteristics of particles derived from industrial activities and motor vehicles in urban areas in Brazil are summarized in Table 2.The most studied sites in articles on emissions of these pollutants were the metropolitan regions of São Paulo and Rio de Janeiro 7,8,90,91,94,95,98,99,102,103,105 .
In metropolitan areas, PM is made up of mainly organic elements 95,100 .In the city of Campinas, São Paulo, studies show that PM 2.5 is made up of 48% elemental carbon and 22% organic carbon 100 .The main organic element was BC, representing 18% to 31% of PM 2.5 in Rio de Janeiro 103 .In the Metropolitan Region of São Paulo, the ionic elements made up 21% of the chemical composition of PM.SO 4 2-, NO 3 and NH + 4 were the most abundant inorganic components in the chemical constitution of PM 2.5 .In the makeup of PM 2.5-10 and PM 2.5 , NO 3 and SO 4 2-represented 60% of the inorganic compounds in PM 2.5 .The concentration of sulphates was 38% higher in fine fractions than in course fractions 98 .
In metropolitan areas in the South and Southeast Regions of Brazil, high concentrations of metals, especially Zn, Pb, Cr, manganese (Mn) and cadmium (Cd) were measured in PM 8,101,102 .In Rio de Janeiro, elevated concentrations of calcium (Ca), magnesium (Mg), Fe, aluminum (Al) and Zn were identified in the elemental composition of PM 2.5 .The presence of Cd, nickel (Ni), Pb and Cu is related to emissions from industry and motor vehicles 102 .In steel manufacturing regions in the state of Rio de Janeiro, Pb concentrations reached values of 140ng/m 3 in the elemental composition of PM 107 .
Polycyclic Aromatic Hydrocarbons (PAHs) were also detected in the chemical composition of PM emitted in metropolitan areas.In Volta Redonda, Rio de Janeiro State, high concentrations of PAHs, such as benzene (52-93µg/m 3 ), toluene (17-30µg/m 3 ) and xylene (1.7-3µg/m 3 ) were found 8 .In the Southern Region of Brazil, in areas with substantial industrial activity, such as Porto Alegre, the mean value of PAHs ranged between 0.04µg/m 3 and 2.3µg/m 3 with  benzo(ghi)perylene (BGP) having the highest concentration 92 .
In the metropolitan region of São Paulo, combustion of diesel and gasoline made up 28% of emissions of PM 2.5 during the winter 7 .In São Paulo, the average level of PM 2.5 was 54µg/m 3 , with a peak of 186.2µg/m 3 between 1996 and 2000 49 .In Rio de Janeiro, the average concentration of PM 10 was 84.7µg/m 3 , with a peak of 199µg/m 3 in 2004 70 .The average level of PM 10 in Rio de Janeiro ranged between 42 µg/m 3 and 169µg/m 3 between 2004 and 2005 102 .

Effects of pollution on the respiratory system
Air pollution studies in Brazil were predominantly conducted in the metropolitan areas of São Paulo and Rio de Janeiro.The results of 18 time-series ecological studies were published, of which eight reported relative risk and 95% confidence interval (95%CI) of hospital admissions and deaths due to respiratory diseases in children and the elderly associated with increments of 10µg/m 3 in the concentration of PM 10 (Figure 1).
Braga et al. 23 evaluated exposure to air pollutants and hospital admissions due to respiratory diseases in children and adolescents (0-20 years old) in São Paulo.The results showed RR = 1.026 (95%CI: 1.022-1.029) in children under the age of 2 and RR = 1.009 (95%CI: 1.001-1.017) in children aged 3-5, associated with increments of 10µg/m 3 with a lag period of 4 days (Figure 1a).Freitas et al. 38 estimated a 1.3% increase (RR = 1.013, 95%CI: 1.010-1.016) in hospital admissions due to respiratory diseases associated with increments of 10µg/m 3 in the concentration of PM 10 (Figure 1a).
With regard to the elderly, the largest relative risk of death due to respiratory diseases was found by Martins et al. 41 .Increments of 10µg/ m 3 of daily levels of PM 10 are associated with a 5.4% increase (RR = 1.054, 95%CI: 1.023-1.086) in mortality due to respiratory diseases in the elderly (Figure 1b).Increments of 10µg/m 3 in the daily levels of PM 10 increased hospital admissions in the elderly due to respiratory diseases by 3.5% (RR = 1.035, 95%CI: 1.012-1.059) in Rio de Janeiro 35 (Figure 1b).In São Paulo, results calculated RR = 1.019 (95%CI: 1.011-1.027)and RR = 1.009 (95%CI: 1.005-1.013)respectively for hospitalization due to respiratory diseases and death due to respiratory diseases in the elderly associated with an increase of 10µg/m 3 in levels of PM 10 36 (Figure 1b).
According to results from a study in São Paulo carried out by Gouveia et al, children show a higher risk of hospitalization due to respiratory diseases than the elderly, with RR = 1.067 (95%CI: 1.049-1.086)associated with an increase of 10µg/ m 3 in the levels of PM 10 35 (Figure 1a).However, the risk of death due to respiratory diseases is higher among the elderly than in children for the same variation in PM 10 levels.With respect to the elderly population over the age of 65 in São Paulo, the percentage increase in the number of deaths was 5.4% 41 .

Discussion and conclusion
Studies show that individuals living in biomass burning areas are exposed to short-term, high concentrations of PM 10 and PM 2.5 whereas individuals living in industrial regions, are chronically exposed to lower concentrations.In metropolitan areas, where peak concentrations of PM are smaller, high levels of pollutants were also found, especially during thermal inversions 15,49,70 .These pollutants include fungal spores, toxins, bacterial products, pollen and endotoxins.The effects of exposure depend not only on the concentration of pollutants, but also on the time of year, duration of exposure and the toxicity of the particles to which an individual is exposed 3,4 .
In terms of adverse health effects, several respiratory problems resulting from the acute inhalation of PM were witnessed in the Southeast Region and in the Brazilian Amazon in both children and the elderly 107,108,109 .Air pollution has a direct effect on the cardiovascular system.Unfortunately however, this effect was not studied in the subequatorial Amazon region.Although, long-term exposure has been shown to be related to a lower life expectancy and increased risk of mortality from cardiopulmonary diseases in urban areas in the United States of America, this effect has still not been investigated in Brazil 2,110 .In contrast, the adverse effects of short-term exposure to PM depends on the degree of toxicity of the physical and chemical characteristics of the emissions source 16 .In terms of particle size, PM 2.5 shows the greatest potential risk to human health resulting from inhalation, deposition and penetration deep into the pulmonary alveoli 4 .Deposition of fine and ultrafine particles, primarily by diffusion, in the respiratory tract increases with decreasing particle size 16 .
This physiological mechanism related to high exposure levels may explain the existence of a considerable number of cases of respiratory disease in some municipalities in the Amazon region, especially in vulnerable children and the elderly.The physical and chemical characteristics of PM 2.5 receive greater attention in the literature in biomass burning areas in the Brazilian Amazon due to the link between the scientific network and the international project the Large Scale Biosphere-Atmosphere Experiment in Amazonia.Unfortunately, few studies related to the adverse health effects of PM 2.5 have been carried out in this region.Source: Gouveia et al. 35 (A); Gouveia et al. 35 (B); Gouveia et al. 49 (C); Gouveia & Fletcher 22 (D); Gouveia et al. 35 (E); Freitas et al. 38 (F); Daumas et al. 42 (G); Martins et al. 41

(H).
Apart from higher concentrations of metals in urban areas, the elemental composition of PM particles released in biomass burning areas was similar to that of particles released in metropolitan areas.In the state of Minas Gerais, in the cities of Ouro Preto and Sete Lagoas, particles showed high concentrations of metals due to the presence of mining and industry sources, but these results were not related to health effects 97,111 .In a recent study by Zanobetti et al. 112 , the mass of PM 2.5 showed high concentrations of arsenic, nickel, chromium and bromine which were associated with increased hospital admissions in elderly residents in 26 cities in the United States.
PAHs were found in PM in metropolitan regions of Rio de Janeiro and Porto Alegre and showed genotoxic effects 8,92 .In regions where biomass burning occurs, PAHs receive little attention in the literature, but one study in the Brazilian Amazon found the presence of various hydrocarbons with potentially carcinogenic effects: fluoranthene, benzo(a)anthracene, benzo(e) pyrene indeno-(cd)pyrene, dibenzo(ah)anthracene and benzo(a)pyrene 113 .
With respect to the organic composition of PM, BC stands out as the main chemical constituent of particles released in biomass burning areas, where higher concentrations are experienced in fires areas, and urban areas.A study carried out in the Amazon biome during the 1995 dry season shows peak concentrations of BC in fine particulate mass at levels (17.5µg/m 3 ) that exceed annual levels of PM 2.5 acceptable for human health 3,76 .BC is associated with known trace elements of emissions from burning such as S, K, Cl, Ca and Zn 6 .It has the capacity to absorb radiation and is the principle factor in the reduction of visibility caused by air pollution 114 .Experimental and epidemiological studies show that exposure to ultrafine particles of BC are associated with increases in inflammatory cells, reduced alveolar macrophage activity and cardiovascular disease 115,116 .
For all emission sources, SO 4 2-was the most highly concentrated element of all the inorganic components of PM 2.5 .This formation of sulfates involves the conversion of SO 2 to sulfuric acid (H 2 SO 4 ) 117 .Experimental studies show that acute exposure to H 2 SO 4 produces inflammatory responses in humans and animals 3,4,118 and its corrosive characteristics may influence PM 2.5 lung deposition and lung compartment clearance rates 117 .
Eventually, at low temperatures, H 2 SO 4 is neutralized by the presence of ammonia (NH 4 ).Thus, in areas in the Amazon region, lower NH 4 deposition rates during the dry season could lead to increases in the availability of H 2 SO 4 in fine fractions of PM 2.5 , so increasing adverse health effects 88 .However, in urban areas, due to the number of motor vehicles, emissions of SO 2 are higher than in biomass burning areas, contributing to the formation of H 2 SO 4 .
Studies project an annual growth rate of 3.5% in sales of smaller vehicles through to 2015 and of 2.2% as from 2016, leading to increases of SO 2 , NO 2 and PM emissions 119 .The studies that detected a link between daily changes in PM and daily mortality generally showed that the effects were greater in the elderly and among individuals with selected underlying diseases.Several epidemiological studies have associated daily levels of these pollutants with cardiopulmonary effects 49,55,70 .Research on exposure to multipollutants has been widely conducted with respect to PM and the adverse health effects associated with constituents of particulate mass 5,67,112 .However, adverse effects from simultaneous exposure to all these pollutants have gained little attention in Brazil.
Several time-series studies were conducted in metropolitan areas to investigate the health effects of air pollution 21,22,23,27,28,31,32,35,36,38,41,42,44,46,49,64,69,74 .Published in 2007, the first studies on the health effects of air pollution in biomass burning areas in the Brazilian Amazon were limited to descriptive studies and focused mainly on asthma 59,61,65,66,72 .Time-series studies conducted in the subequatorial Amazon showed that daily levels of PM 2.5 measured during the peak of the dry season led to an increase in the percentage of hospital admissions and outpatient visits due to respiratory diseases in children and the elderly 107,109 .These results corroborate with those observed in the Southeast Region of Brazil in areas where sugarcane burning occurs 52 .
Time-series studies are essential to investigate the acute health effects of air pollution.However, certain limitations of study design make it difficult to estimate uncertainties surrounding environmental factors, exposure and outcome.Individual details are not included in the analysis and it is possible that some outcomes may include the effects of exposure to other pollutants and factors 36,120 .Longitudinal and experimental studies with a more detailed analysis of exposure and outcome at the individual level and multiple air pollutants could reduce uncertainties related to the effects of atmospheric particulates on health.
Children, one of the groups that are most sensitive to the effects of air pollution, showed greater susceptibility to respiratory problems due to variation in PM levels.This is due in part to the influence of children's anatomical and physiological characteristics on the deposition and removal of inhaled particles 121 .Moreover, immunological immaturity interferes with recovery from damage caused by pollution 122 .
The fractions of PM deposited in the tracheobronchial region can be removed during the first 24-48 hours by mucociliary activity 123 , whilst the particles that reach the alveolar regions are only cleared, preferably by the action of macrophages or by alternative mechanisms, after a period of weeks or even months 124 .Therefore, individuals exposed to higher concentrations of PM living in areas where biomass burning lasts on average for only three months of the year (in the Brazilian Amazon for example) may experience better physiological recovery than those individuals in urban areas who are subject to constant exposure.
This overview of Brazilian anthropogenic sources of exposure to air pollution is dependent on the availability and quality of information found in scientific databases in the public domain.The differences in methodologies used by these studies to measure exposure and the physical and chemical characteristics of anthropogenic sources of air pollutants may limit the comparison of results.However, based on the concordance between results, considerations may be made on the physical and chemical characteristics of the pollutants and the adverse effects of air pollution on health.It should be noted that this is a systematic overview and not an exhaustive review of current data.Only selected areas related to human health have been discussed.
This systematic review suggests that the exposure-response relationship between daily changes in PM aerosol and daily outcomes differs between Brazilian biomass burning areas and metropolitan areas in terms of time, duration and toxicity of particles.In general, the data consistently shows that the current Brazilian air pollution standards 125 are not protecting human health from exposure to air pollution in metropolitan and biomass burning areas .Clearly, these standards may be considered "unhealthy", suggesting that the Brazilian government and private sector need to discuss and establish specific standards and regulations for PM 2.5 .The São Paulo government is currently considering standards, however, national legislation to address the protection of human health on a countrywide basis is necessary.
In conclusion, the results of these studies on the effects of air pollution on health are specific to the study area and may not be applicable to areas with different anthropogenic emission sources.In Brazil, children are the group that is most sensitive to hospitalizations and deaths due to respiratory diseases followed by the elderly.However, there is a need for further study of the health effects of PM in the Brazilian Amazon.Although epidemiological studies have demonstrated a relationship between PM aerosol and its detrimental effects on health, these associations are fraught with uncertainties due to methodological limitations and the synergistic effects of environmental factors and pollutants and the physical ramifications of PM.
Poluentes Ambientais; Poluentes do Ar; Material Particulado; Doenças Respiratórias Contributors B. F. A. Oliveira contributed to the analysis of the bibliographical references from the database search, structuring and drafting of the article and discussions on preparing the article.E. Ignotti and S. S. Hacon collaborated in the review and selection of the publications, and in the revision of the article.

Figure 1 Studies
Figure 1Studies with relative risk and 95% confi dence interval for hospital admissions and death from respiratory diseases in children (1a) and the elderly (1b), associated with 10µg/m 3 increments in PM 10 levels in Brazil between 2000 and 2009.

Table 1
Articles on the physical and chemical characteristics of pollutants from biomass burning in Brazil published between 2000 and 2009.

Table 2
Articles on the physical and chemical characteristics of pollutants from industrial activities and vehicles in Brazil published between 2000 and 2009.

Table 3
Studies on air pollution and health effects conducted in urban and biomass burning areas, according to location, study type, subject group and respiratory health outcomes published in Brazil between 2000 and 2009.