Thanks to sustained efforts in epidemiological research, we now know that: a) high concentrations of particulate matter (PM) in the air we breathe are the primary factor of health hazards tied to air pollution and b) that the finer the particles are (2.5 micrograms in diameter or smaller), the greater the danger. Most epidemiologists make the case by looking at mortality rates and causes. For example, the American Heart Association has shown time and again that in contexts of environmental pollution due to elevated PM concentrations, people tend to die of respiratory, cardiovascular, and oncological pathologies in greater numbers than normal [1]. Likewise, another important case in the international literature centered on particulate matter with a diameter of 2.5 micrograms (PM 2.5) shows that each concentration increments equal to 10 micrograms per cubic meter (10 μg/m3) corresponds to a 6 % increase in death due to cardio-pulmonary disorders and an 8 % increase in death due to lung cancer [2].

Moreover, research focused specifically on environmental pollution due to industrial production has shown that different industries and manufacturing processes produce particulate matter of different size. When it comes to the steel industry in particular, the literature shows that the processing of iron and other heavy metals, which constitutes the first step of steel manufacturing, produces dust emission with heavy polluting consequences in some area [3–5].

Research focused on industrial pollution from an occupational health standpoint is also of guidance in methodological terms, since it tends to assess risk based on data like respiratory conditions rather than mortality rates. In particular, a number of studies investigating the health hazards tied to occupational dust exposure rely on a combination of medical questionnaires and analysis of lung function through spirometry testing [6, 7].

This approach is especially useful for general population studies based on contexts where death records are either inaccessible or incomplete, for instance due to heavy migration flows. This is precisely the case of our research setting: Piquiá de Baixo, a neighborhood in the city of Açailândia, state of Maranhão, in north-eastern Brazil, where people have shared their vital space with an iron-processing plant tied to the international steel industry since the late 1980s. Faced with resistance from the state and local health board in accessing records and with incomplete information when access was granted, we could not rely on illness and mortality rates to investigate the potential health risks tied to environmental pollution caused by the industrial plant. We thus decided to follow the example of the above-mentioned studies and assess the health conditions of the local population based on medical history questionnaires and the assessment of pulmonary function via spirometry testing, using advanced technology and following the latest international guidelines. The main objective of our investigation is to contribute to the literature on the health risks associated with fine particle pollution (PM 2.5 or smaller) with data from Brazil.

The sample is constituted of 220 subjects out of a target population of 669; exclusion from the study was due to: unavailability for 434 subjects (most of whom were men and mostly due to work reasons), refusal to take the simple spirometry test in the case of 11 subjects, and infective contraindications for four subjects.

The average age was 31 ± 15 years and there was an overall prevalence of women (62 %).

The spirometric testing of lung functions carried out on a sample population of 220 Piquia residents - a community in Brazil known to be exposed to high levels of air pollution produced by a local iron processing complex- yielded abnormal results in 28 % of the sample. We consider this to be an extremely significant percentage from a medical standpoint, both in terms of sample demographics and compared to results found in similar studies.

In fact, our sample represented a cohort of young adults (mean age: 31 years old), an age group that generally reports very low rates of spirometric abnormalities, among which the percentage of smokers was comparable to the national average for Brazil [17].

In comparative terms, the European Community Respiratory Health Survey (ECRHS) is a significant reference. The study was carried out in the early 1990s based on general population samples in the 20-44-year-old age group in Europe and several non-European countries. According to the study, the prevalence of diagnosed bronchial asthma ranged from 2 % in Estonia to 11.9 % in Australia [18]. More recent data from the USA revealed a 2.6 % incidence of such as chronic obstructive pulmonary disease (COPD) in the 18-34-year-old age group [19]. If we sum the older ECRHS data with the more recent USA data, we get an age group comparable to that of our study (18 to 44), in which obstructive or mixed alterations of respiratory functions ranges from 4.6 to 14.5 % – well below the 28 % incidence rate we found.

The prevalence of spirometric abnormalities yielded by our study remains significantly high also when compared to USA national data focused on the idiopathic pulmonary fibrosis. In fact, among rare respiratory diseases, idiopathic pulmonary fibrosis is the most common associated with a restrictive spirometric footprint. According to Raghu et al. [20], cases of the pathology diagnosed based on restrictive criteria range between less than 0,005 % and less than 0,028 % (from 14 to 27.9 every 100,000 residents). A limitation of our study lies in not having measured the static lung volumes and there are disputes about the spirometric classification of respiratory alterations to restrictive footprint rather than obstructive [21].

The significance of spirometric abnormalities associated with disorders of a restrictive kind in the cohort of Piquià residents we analyzed (19.5 % of the sample) is especially difficult to explain, since to date there are no published epidemiological studies from Brazil focused on restrictive lung disorders. However, we have grounds to believe that it is strongly correlated with the situation of heavy air pollution caused by the industrial complex. In fact, the presence of fine particles in the air we breathe is associated with a significant drop in respiratory function; and the air quality in Piquiá de Baixo is compromised by the emissions of fourteen blast furnaces that run on continuous cycle without filtering, plus the general polluting effects of the overall production cycle revolving around the local industrial complex.

As regards fine particle pollution a recent study entitled ESCAPE (European Study of Cohorts for Air Pollution Effects) found that every 10 microgram increment per square meter (10 μg/m³) in the concentration of PM10 corresponded to a significant drop in the respiratory function of test subjects, quantified as follows: a 44.6 ml decrease in FEV₁ and a 59.0 ml decrease in FVC, both expressed as absolute value [22]. Recently, another study showed how exposure to ambient air pollution is associated with restrictive ventilatory patterns [23].

As regards spirometric abnormalities associated with obstructive respiratory defects in our population sample, we can advance a more accurate interpretation based on regional and national data for pathologies of this kind. The rate of obstructive abnormalities we found (10.5 %) is close to the one found among Maranhão adolescents, which is 12.7 % [24], and to the national average incidence of asthma in Brazil, which is 8.5 % (albeit with significant differences between the south, 12.6 %, and the north-east, 4.4 %) [25]. In addition, high concentrations of PM10 have been proven to be strongly correlated to increases in hospitalization due to asthma attacks also in Brazil [26].

We acknowledge the limitations of our study, beginning with the limited representativeness of the sample, given its small size. This was mainly due to the impossibility to collect sufficient data from adult male residents due to work-related reasons: as the demographic group with greater employment opportunities, in fact, most men were unavailable for programmed home visits and spirometry test sessions. In light of the fact that employment rates in the community are higher among men than women and that many residents work in the iron processing complex or in connection with it, exposure to polluting substances deriving from iron processing is potentially higher precisely among men; in other words the demographic group for which our study is poor in data. This means that the prevalence of spirometric abnormalities and therefore of respiratory problems in the neighborhood population could be even higher than recorded.

We are also aware that our data does not support direct conclusions on a direct cause-effect relationship between pollution generated from Piquià’s iron-processing plant and the spirometric abnormalities recorded in the local population. In fact, there are various causes that could concur with the pulmonary problems we documented, like the presence of other sources of air pollution, namely fine particles issuing from the trucks that transit on the highway junction road carrying raw and processed material, and the socio-economic context of the local population, as proven by studies that correlate poverty to lower respiratory development [27].

Except for this last potential causal factor, however, we note that both the pollutants produced by blast furnace emissions and those released by the transportation of raw and processed materials to and from the Piquià industrial complex are connected to the presence of steel companies in the area. In a logic of prevention, we thus think it is of fundamental importance to assess, address, and remove all causes of fine particle pollution in Piquia.

Moreover, we would like to point out that our study relies on spirometric abnormalities to evaluate the effects of industrial pollution on pulmonary functions and does not consider the potential correlation between fine particle pollution in the area and higher than normal incidence values of cancer pathologies in general and lung cancer in particular among the local population. Unfortunately, we could not inquire into this cause-effect relationship in the population under analysis, due to lack of specific records in the local health system regarding the incidence of lung cancer. However, given that several studies correlate the annual PM average to the incidence of lung cancer [2, 28], this correlation is likely to exist in Piquià as well.

In closing, the clinical data here reported, the lack of inspections and epidemiological records on the part of the public health system, and the particular environmental characteristics of the Piquia area documented by several court-mandated reports and surveys, lead us to define the Piquià case as emblematic of how the lack of health and environmental policies targeting industrial production results in severe impact on the health conditions of populations that reside in close proximity to processing plants tied to the steel industry.

This independent study suggests that air quality in Piquiá de Baixo is likely to have a relevant impact on the respiratory health of local residents. Aside from the significant rate of lung function abnormalities we have recorded, research on the health conditions of populations that reside next to industrial steel processing plants alone justifies the need for urgent action to protect Piquiá de Baixo residents from the extremely high levels of pollution they are exposed to. Along with an immediate emergency response to redress the health hazards that threaten men, women, and children in the area (such as collective relocation) we believe that further action should be taken a) to improve the standards of industrial production in the Piquia industrial area, to reduce the effects of fine particle pollution and b) to raise greater awareness in this region of the Maranhão state regarding the connection between air quality and the health conditions of local residents and steel workers, following the example of similar programs implemented elsewhere in Brazil and South America [29].