Occupational exposure to air pollutants: particulate matter and respiratory symptoms affecting traffic-police in Bogotá
Exposición ocupacional a contaminantes atmosféricos: material particulado y síntomas respiratorios en policías de tránsito de Bogotá.
Jesús A. Estévez-García1, Néstor Y. Rojas-Roa2 y Alba I. Rodríguez-Pulido3
1 InstitutoNacional de Salud, Bogotá, Colombia. firstname.lastname@example.org
2 Department, Engineering Faculty. Universidad Nacional de Colombia. Bogotá, Colombia. email@example.com
3 Toxicology Department, Medicine Faculty. Universidad Nacional de Colombia, Bogotá, Colombia. firstname.lastname@example.org
Received 19th February 2013/Sent for Modification 20th March 2013/Accepted 22th April 2013
Objectives Quantifying personal exposure to particles less than 10 micrometres in diameter (PM10) and determining the prevalence of respiratory symptoms in traffic-police officers working in Bogotá's metropolitan area.
Methods This was a cross-sectional study of 574 traffic-police officers divided into two groups (477 traffic-police and 97 police working in an office). They were given a questionnaire inquiring about respiratory symptoms, toxicological medical evaluation, lung function tests and personal PM10 monitoring. The differences between groups were found using stratified analysis (i.e. comparing odds ratios). Multivariate analysis of factors related to symptoms and diagnosis of respiratory alteration was also performed.
Results Respiratory symptoms concerned a higher prevalence of cough, expectoration and rhinosinusitis in the traffic-police group. Medical examination revealed that the traffic-police group had higher nasal irritation prevalence; lung function tests showed no difference. Mean PM10 levels were higher for the traffic-police group (139.4 μg/m3), compared to the office work group (86.03 μg/m3).
Discussion PM10 values in both groups did not exceed allowable limits for respirable particles in the workplace according to ACGIH standards. Traffic-police exposed to air pollution had an increased risk of developing respiratory symptoms and signs, thereby agreeing with the results of this and other studies. Personal monitoring is a valuable tool when quantifying the concentration of PM10to which an individual has been exposed during a normal workday. This study contributes towards further research in to the effects of PM10 in populations at risk.
Key Words: Air pollution, signs and symptoms, respiratory tract disease, particulate matter, traffic-police officer, occupational exposure (source: MeSH, NLM).
Objetivos Cuantificar la exposición personal a partículas menores de 10 micras (PM10) y determinar la prevalencia de síntomas respiratorios en policías de tránsito que trabajan en el área metropolitana de Bogotá.
Métodos Estudio transversal de 574 policías divididos en dos grupos (477 policías de tránsito y 97 policías de oficina). Se les aplicó cuestionario sobre síntomas respiratorios, evaluación médica toxicológica, pruebas de función pulmonar y monitoreo personal a PM10. Las diferencias entre los grupos se hallaron mediante análisis estratificado y calculo Odds Ratio. Se realizó análisis multivariado de factores relacionados con los síntomas y diagnósticos de alteración respiratoria.
Resultados Síntomas respiratorios como tos, expectoración y rinosinusitis tuvieron mayor prevalencia en los policías de tránsito. El examen médico mostró mayor prevalencia de signos de irritación nasal en los policías de tránsito. Pruebas de función pulmonar no mostraron diferencias. Los niveles promedio de PM10 fueron mayores en el grupo de tránsito (139,4 g/m3) comparados con el de oficina (86,03 g/m3).
Discusión Los valores de PM10 en ambos grupos no exceden los límites permisibles de partículas respirables en el lugar de trabajo por la ACGIH. Los policías de tránsito expuestos a la contaminación del aire tienen mayor riesgo de desarrollar síntomas y signos respiratorios, como lo muestran este y otros estudios. El monitoreo personal es una herramienta valiosa para cuantificar la concentración de PM10a la cual un individuo está expuesto durante la jornada laboral. Este estudio contribuye a una mayor investigación sobre los efectos de PM10 en las poblaciones en riesgo.
Palabras Clave: Contaminación del aire, material particulado, policía, exposición profesional (fuente: DeCS, BIREME).
Air pollution is a form of environmental degradation which has become widespread regarding economic and population growth. Such environmental degradation leads to public health consequences, thereby causing diseases impairing community welfare (1,2). A relationship between PM10 exposure and negative effects on health leading to respiratory and cardiovascular morbidity and mortality has already been established (3,4). Larsen found that the average annual cost of air pollution regarding health in Colombia was nearly 1 % of national GDP, 65 % being associated with mortality and 35 % with morbidity (5). More than 1.2 million vehicles circulate in Bogotá, representing the main source of atmospheric emission (70 %); this leads to more than 2,200 tons of PM10 and other pollutants being produced annually (6). Exposure has only been quantified at fixed monitoring stations in many countries and this does not provide a reliable correlation between individual exposure and outcomes (7, 8). Long-term studies have shown that every 10 μg/m3 increase in PM10 concentration is associated with an increase of around 5 % regarding the risk of cardiopulmonary mortality and 8 % lung cancer (9). There is a lack of research in Colombia regarding environmental pollution's toxic effects on occupationally-exposed groups; the present study shows how quantifying individual exposure to PM10 through personal sampling was correlated to respiratory tract symptoms and abnormal clinical findings in lung function tests in a population having great exposure to this pollutant (i.e. traffic-police officers).
Study population and design
This was a cross-sectional study which lasted one year on a sample of 574 police officers working in the metropolitan area of Bogota. Traffic-police were defined as being the exposed group, regarding their operational duties (477 police officers), and police having administrative functions (97 office police) formed the less exposed or control group. The sample was based on the prevalence for respiratory symptoms (cough) for individuals who were occupationally exposed to PM, according to previous studies (10). These police agents were working in twelve operational areas and formed five special groups: environmental control, bus and airport terminal control, road construction group, mass transit system control and police officers working at the tolls on the city's limits. Inclusion criteria required the officers to be volunteers and that they had signed the informed consent form. The study complied with international and national ethical health research standards and was granted approval by the Universidad Nacional de Colombia's the School of Medicine's ethics committee and the Colombian Police Health Department's equivalent body.
Sampling PM10 levels
Personal PM10 measurement and sampling strategy involved using the methodology recommended by the US National Institute for Occupational Safety and Health (NIOSH) (11). Calibrated and certified battery-operated pumps were used for personal sampling (MSA Escort ELF and Apex Pro Casella). The devices were carried during working hours and flow-rate sampling was checked with a flow-meter at the beginning and end of each shift. PM10 concentrations, obtained from the city's network of air quality monitoring stations, were calculated by applying correction factors for environmental variables (humidity and barometric pressure)for the day and area where the respective sampling was made. The measurements were compared with PM10 occupational exposure limits established by the American Conference of Governmental Industrial Hygienists (ACGIH).
An amended version of the American Thoracic Society's Division of Lung Disease (ATS-DLD-78) health status questionnaire was used; this requests data concerning demographic variables, the presence of respiratory symptoms, family medical history, occupational exposure to substances causing respiratory disorders, smoking index, exposure to indoor sources of pollution, the use of respiratory protection devices and current employment history.
Toxicological medical evaluation
The participants' clinical status was individually assessed regarding vital signs, anthropometric measurement, otorhinolaryngology and a review of the officers' rib cages, emphasizing cardiovascular and respiratory systems. Clinical signs of ocular and nasal irritation were also evaluated.
Lung function test
A portable spirometer (Jaeger) was used by qualified personnel at the end of the workday, following ATS spirometry criteria and standardization procedures; vital capacity (VC), forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and the CVF/VEF1 ratio were evaluated. These volumes were evaluated at baseline and after bronchodilator administration. Spirometric measurements were interpreted by blinded assessment by an expert on the subject (pulmonologist) for the final report.
Respiratory disorder diagnosis
A diagnosis of lower respiratory tract disorder was defined as being a report of a respiratory symptom (cough, expectoration, wheezing or dyspnea) and/or the presence of clinical signs of impaired breathing (stridor, wheezing, crackles) and/or the presence of spirometric impairment. A diagnosis of upper respiratory tract impairment was defined as being a reported upper respiratory symptom (runny nose, nasal itching, throat clearing, facial pain, etc.) and/or presence of clinical signs of upper respiratory tract disorder (nasal mucosa hyperaemia, profuserhinorrhoea, turbinate hypertrophy, nasal bleeding or stigmata of bleeding, pale nasal mucosa, facial pain on palpation of sinuses, runny posterior epistaxis, oropharynx failure).
SPSS 18.0 for Windows (Chicago, IL, USA) and STATA 9.0.) was used for analyzing the data; Chi-square or Fisher's exact tests were used for finding differences between categorical characteristics' frequency between groups. The F test was used to find differences between the groups' average values. Bivariate analysis involved finding differences between exposed and control groups concerning respiratory symptoms using stratified analysis by estimating and comparing odds ratio (OR), with the respective 95 % confidence interval (95 % CI). Multivariate analysis (logistic regression model) weighed each factor regarding the outcome or degree of association. A p-value below 0,05 was considered statistically significant.
Most of the 574 individuals evaluated were male (average age = 29.9 years-old);there were statistically significant differences between groups regarding gender and educational level (i.e. categorical variables). Higher average age, length of time residing in Bogota and seniority were found in the police office-based group.
The exposed group had greater prevalence regarding a record of respiratory disease (bronchitis, pneumonia, asthma and tuberculosis) (15.5 % cf 10.5 %) and higher frequency concerning a history of occupational exposure to dust, gases and smoke (40.2 % cf 31.2%) compared to office-based police. Natural gas was the most widely used fuel in the agents' homes. The use of personal respiratory protection devices was very low in both study groups (Table 1).
Respiratory symptoms and diagnosis
Regarding respiratory symptoms, the traffic-police group had a higher prevalence of cough (18.6 % cf 6.2 %; OR 3.4: 1.5-8.2 95 % CI) and expectoration (19.9 % cf 8.2 %; OR 2.8:1.3-5.9 95 % CI). Reports of lower respiratory tract symptoms were higher in the traffic-police group compared to the office group (37.1 % cf 30.9 %; OR1.3: 0.8-2.1 95 % CI). The traffic-police group had more prevalent diagnosis of lower (58.7 % cf 48.5 %; OR1.5: 0.9-2.3 95 % CI) and higher respiratory disorder (79.7 % cf 72.2 %; OR1.5: 0.9-2.5 95 % CI); however, no statistically significant differences were found (Table 2).
Toxicological medical assessment
The exposed group had a high prevalence of ocular irritation (32.9 %; OR 6.3: 2.8-13.9 95 % CI) and signs of nasal irritation (62.3%; OR3.7: 2.3-5.9 95 % CI) compared to controls (Table 2).
Lung function test
The exposed group suffered more spirometric changes (8.4 %; OR1.5: 0.9-2.4 95%CI), this being the most common obstructive pattern for both groups. Post-bronchodilator spirometry pattern suggested airway irritability syndrome in 29.4 % of the exposed group and 29.9 % ofthe control group (OR 0.97:0.6-1.6 95 % CI) (Table 2). There were no statistically significant differences between the study groups regarding mean values for lung function parameters (FVC, FEV1, CVF/VEF1, CV) during pre-orpost-bronchodilator spirometry (Table 1).
Average PM10 value was higher in the exposed group (139.4±76.5 μg/m3) than in the control group (86.0±29.8 μg/m3), the difference being statistically significant (Table 1). None of the measurements exceeded the permissible occupational exposure limit proposed by the ACGIH (3 mg/m3). PM10 monitoring of work areas revealed the highest concentrations in area 8 (242.9 μg/m3), the road construction group (180.1 μg/m3), those working at the bus terminal (161.3 μg/m3) and in area 7 (176.6 μg/m3). The average overall exposure values regarding work shift were higher for afternoon working hours (139.4 mg/m3), followed by the morning (136.1 μg/m3) and night (111.2 μg/m3) (Table 4).
Analysis of smoking. Smoking prevalence was higher in the exposed group (42.3 % cf 36.1 %). The results were included in multivariate analysis for adjusting the degree of association regarding other variables to enable studying this factor's influence.
Smoking was associated as a risk factor regarding a diagnosis of lower respiratory tract disorder (OR1.4: 0.8-2.4 95 % CI); however, there was no statistical significance. Belonging to the exposed group, being male, having a history of lung disease and being a smoker were also statistically associated with symptoms and diagnosis. PM10 concentration was not significantly associated with outcome in the multivariate model. Seniority and age were significantly associated with symptoms such as cough and dyspnoea in multivariate analysis.
The study's findings were consistent with reports in the pertinent literature concerning the negative effect of environmental exposure at work to air pollutants, thereby validating the present results. Traffic police had a higher prevalence of respiratory symptoms, such as cough and expectoration, these being similar findings to those reported by Karita in 2001 who contrasted occupational exposure to different levels of PM10 in three police groups in Bangkok (10). It was found that the prevalence of cough (12.8 %), expectoration (24.4 %) and wheezing (3.8 %) was higher in individuals having traffic duties, but their differences were not statistically significant given the small number of subjects in the study groups. Dyspnoea was more prevalent in the control group; this symptom had the same association in our study. Another study in Bangkok by the same authors in 2004 reported a higher prevalence of cough, expectoration, wheezing and dyspnoea in traffic-police compared to the control group and a significant association between smoking and the area where an officer was working (12). A study carried out in 2005 by Ingle in Jalga on (India) found even larger symptom prevalence than the present study, reporting that cough (40 %), dyspnoea (10 %) and upper respiratory tract irritation symptoms (29 %) were the most frequently occurring, compared to a group of healthy workers having different PM10 exposure levels; the strength of symptom association with the highest PM10 levels (traffic-police group) was significant (OR>1) (13). Smoking was deliberately controlled by this study's design as smokers were not included; the association obtained did not relate to this factor. Our study was controlled for smoking in the analysis, a significant association only being obtained with the presence of lower respiratory tract symptoms but not each specific symptom (cough, expectoration, etc.).
A study of traffic policemen in Ankara (Turkey) reported 48 %smoking prevalence (higher than ours) and 53 % lower respiratory tract symptom frequency, such as chest tightness, dyspnoea, cough and chronic cough in the traffic-police group (14). Thippanna conducted a study in Hyderabad (India) in 1999involving 665 traffic-police; the study reported that respiratory symptoms were correlated with the number of years of exposure to air pollution. Individuals having at least 5 years of exposure primarily reported coughing and chest tightness. Symptoms such as allergies, respiratory distress, increased coughing and tightness appeared as age and exposure increased (more than 5 years) (15). The above was seen in our study's multivariate analysis, in which being in the traffic police and being older were significantly associated with symptoms such as cough and dyspnoea. Altered nasal signs were significantly associated with working in the traffic-police. Multivariate analysis suggested that this group had a greater risk of symptoms, such as cough, sputum production and lower respiratory tract symptoms, as well as diagnosis of upper and lower respiratory tract disorders. Such associations corroborated reports in the literature (10,12,13) and revealed that working in the traffic police created risks regarding the aforementioned symptoms. Information bias should be taken into account regarding the results of our study because some people experienced side-effects which they ignored or tried to hide such situation because they expected negative consequences regarding their career chances (16,17). This may have been reflected in the low prevalence for some respiratory symptoms in the highest exposure group. Another aspect concerned healthy-worker bias because such population was subject to a rigorous selection process (ipso facto their income) and their respiratory response physiological mechanisms were better able to adapt to a hostile work environment (18, 19). It should be noted that cross-sectional studies tend to underestimate the prevalence of events, particularly regarding acute symptoms, as outcomes are evaluated during a single moment of time (16,17).
No significant differences were found in our study regarding mean pulmonary function values; this contrasted with that reported by other authors who have evaluated traffic-police as they have found decreased lung function compared to control groups (10,13,15). Low prevalence regarding spirometric changes in populations occupationally exposed to particulate matter has been reported, i.e. Colombian studies on cement workers in 1999 where Giraldo found 92 % normal spirometry (20). The FEV1 pulmonary function and 25 % peak expiratory flow rate regarding vital capacity (V25) were significantly lower in traffic-police compared to officers in rural areas in a study conducted in Bangkok in 2001(10). Multiple regression analysis showed that age and job-site were significant factors in explaining variations in FEV1 and V25 (smoking making no significant contribution to such variation) (10). A study in Jalga on (India) fixed samplers in high traffic density roads, average224 μg/m3 values being obtained which exceeded that country's PM10 air quality standards (120 μg/m3) (13). Monitoring in our study involved using personal samplers and reflected lower average concentrations than those found by another study in India. Although the two studies evaluated similar occupational groups (traffic-police), the parameters for determining whether exposure levels came within permissible ranges were different, as were the measurement methodologies. Exposure levels in our study came within the permissible occupational limits proposed by the ACIGH. However, Colombian air quality standards for the general population regarding PM10 (150 μg/m3) were exceeded in some areas, and the scientific evidence has shown toxic effects even with particulate levels below air quality standards, including those set by the World Health Organization.
It is worth noting the approach of other studies, such as that by Watts in 1995, which have highlighted monitoring personnel's crucial role in determining health effects attributed to different air pollutants(8). The personal measuring PM10 in traffic-police for two weeks in this study reported higher concentrations than those provided by fixed monitoring stations, this being consistent with that found by other studies, such as that by Violante (2006) or Lioy (1990) (7,21). The concentrations obtained by Watts in 1995 were similar to those found in our study, although not comparable, given the conditions in each work environment which may have altered PM10 chemical composition and its toxic effect on health (14,22).
Personal monitoring is a valuable and reliable tool when quantifying the concentration of PM10 or the dose to which an individual has been exposed during their workday, and relating it to the presence of respiratory outcomes, regarding many environmental factors and an individual's type of activity leading to variability between and within work areas (micro) and different days. Regarding domestic risk factor, natural gas was used most frequently in the agents' kitchens; this fuel represents a low source of PM production. However, households lacking adequate technical conditions concerning their gas appliances can be sources for other pollutants being produced, such as carbon monoxide, which can cause neurological and cardiovascular injury. Factors such as a high prevalence of smoking, personal pulmonary history, combined with chronic exposure to doses above permissible PM10 limits are multi-causal risk factors for developing respiratory health disorders in such an occupationally-exposed population. Ideally, the PM10 sampled here should be characterised to determine each monitored environments' chemical components. This leads to debate about the adequacy of air-quality standards for protecting public health and, equally, assessment of populations occupationally-exposed to air pollutants, not only in such work-related environment, but also to settings outside their work. List of abbreviations: PM, particulate matter; RSP, respirable particle; VC vital capacity; FVC, forced vital capacity; FEV1, forced expiratory volume in one second; GDP, gross domestic product.
Acknowledgements: We would like to thank the Colombian Police's Health Department and Traffic and Transport Department, Bogota's Metropolitan Police Traffic Commanders and Occupational Health Group for their collaboration during the study. We would like to thank the Universidad Nacional de Colombia's Research Office (Bogotá) and Bogota's Environmental Protection Agency (Secretaría de Ambiente de Bogotá) for their funding and we would also like to thank Universidad Nacional de Colombia Toxicology Department staff (in Bogotá) for their support.
Competing interest: None.
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