Elemental concentrations of ambient particles and cause specific mortality in Santiago, Chile: a time series study

Valdés Ana, Zanobetti Antonella, Halonen, Cifuentes Luis, Morata Diego, Schwartz, Schwartz Joel

Description

The health effects of particulate air pollution are widely recognized and there is some evidence that the magnitude of these effects vary by particle component. We studied the effects of ambient fine particles (aerodynamic diameter < 2.5μm, PM 2.5 ) and their components on cause-specific mortality in Santiago, Chile, where particulate pollution is a major public health concern. Methods Air pollution was collected in a residential area in the center of Santiago. Daily mortality counts were obtained from the National Institute of Statistic. The associations between PM 2.5 and cause-specific mortality were studied by time series analysis controlling for time trends, day of the week, temperature and relative humidity. We then included an interaction term between PM 2.5 and the monthly averages of the mean ratios of individual elements to PM 2.5 mass. Results We found significant effects of PM 2.5 on all the causes analyzed, with a 1.33% increase (95% CI: 0.87-1.78) in cardiovascular mortality per 10μg/m 3 increase in the two days average of PM 2.5 . We found that zinc was associated with higher cardiovascular mortality. Particles with high content of chromium, copper and sulfur showed stronger associations with respiratory and COPD mortality, while high zinc and sodium content of PM 2.5 amplified the association with cerebrovascular disease. Conclusions Our findings suggest that PM 2.5 with high zinc, chromium, copper, sodium, and sulfur content have stronger associations with mortality than PM 2.5 mass alone in Santiago, Chile. The sources of particles containing these elements need to be determined to better control their emissions.

Sujets

• Air pollution
• Mortality
• Particulate
• Elements

Informations

• Publié par: biomed
• Publié le: 01 janvier 2012
• Nombre de lectures: 9
• Langue: English

Extrait

Valdés et al. Environmental Health 2012, 11:82
http://www.ehjournal.net/content/11/1/82
RESEARCH Open Access
Elemental concentrations of ambient particles
and cause specific mortality in Santiago, Chile: a
time series study
1,2* 3 3,5 4 6 3Ana Valdés , Antonella Zanobetti , Jaana I Halonen , Luis Cifuentes , Diego Morata and Joel Schwartz
Abstract
Background: The health effects of particulate air pollution are widely recognized and there is some evidence that
the magnitude of these vary by particle component. We studied the effects of ambient fine particles
(aerodynamic diameter < 2.5μm, PM ) and their components on cause-specific mortality in Santiago, Chile, where2.5
particulate pollution is a major public health concern.
Methods: Air pollution was collected in a residential area in the center of Santiago. Daily mortality counts were
obtained from the National Institute of Statistic. The associations between PM and cause-specific mortality were2.5
studied by time series analysis controlling for time trends, day of the week, temperature and relative humidity. We
then included an interaction term between PM and the monthly averages of the mean ratios of individual2.5
elements to PM mass.2.5
Results: We found significant effects of PM on all the causes analyzed, with a 1.33% increase (95% CI: 0.87-1.78)2.5
3in cardiovascular mortality per 10μg/m increase in the two days average of PM . We found that zinc was2.5
associated with higher cardiovascular mortality. Particles with high content of chromium, copper and sulfur showed
stronger associations with respiratory and COPD mortality, while high zinc and sodium content of PM amplified2.5
the association with cerebrovascular disease.
Conclusions: Our findings suggest that PM with high zinc, chromium, copper, sodium, and sulfur content have2.5
stronger associations with mortality than PM mass alone in Santiago, Chile. The sources of particles containing2.5
these elements need to be determined to better control their emissions.
Keywords: Air pollution, Mortality, PM , Elements2.5
Background between 2.5-10μm, coarse particles) [4,5]. Regional and
Particulate air pollution is a main environmental risk seasonal differences in the health effects of particles have
factor for human health, and short-term associations also been reported [6-8]. Composition of also
between mortality and particulate pollutants are well varies by season, suggesting this may play a role in the
established [1-3]. Many studies have suggested that the toxicity of particles. Due to the lack of data on
parmagnitude of the association between mortality and par- ticulate composition, the health effects of specific
particles differs by particle size, with fine particles (particles components have not been widely studied, and
with aerodynamic diameter less than 2.5μm, PM ) most epidemiological studies performed on a population2.5
having greater effects than larger particles (diameter level are from the United States [9-12]. Studies that
control for seasonal temperature as a surrogate for
ventilation rate have identified sulfur, nickel, and vanadium as
* Correspondence: [e-mail]
1 particularly toxic [9-11], while studies that ignored con-Laboratoire de Géosciences Environnement Toulouse (GET), Observatoire
Midi-Pyrénées, 14, Avenue Edouard, Belin, 31400, France founding by seasonal temperature have reported more
2
Departamento de Geología Aplicada, Servicio Nacional de Geología y
mixed results [13,14]. By identifying the elements most
Minería de Chile, Avenida Santa María 0104, Providencia 7520405, Santiago,
toxic to human health, we can move to more efficientChile
Full list of author information is available at the end of the article
© 2012 Valdés et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.Valdés et al. Environmental Health 2012, 11:82 Page 2 of 8
http://www.ehjournal.net/content/11/1/82
regulations for particulate matter. Therefore confirming [18,22,23], one of the seven air quality monitoring
statheseassociations,particularlyinotherpartsoftheworld, tions of the Automatic Monitory of Atmospheric
Conis important. taminants Network (MACAM NETWORK). This station
In Santiago, Chile, air pollution is a major public is located in a residential area in one of the main green
health concern because of its dense population and the areas in the center of Santiago. East of the station is the
geography of the area [15]. The city is located between Principal National Route “Carretera Panamericana" and
the Andean Cordillera at the East, and Coastal Range at to the west is the University of Chile Campus.
Additionthe West. In the Central Valley of Chile, during the ma- ally, in three of the stations temperature, humidity, solar
jority of the year there is a thermal inversion layer. Dur- irradiation and wind direction are measured [24].
ing autumn and winter, this layer is produced as a result Particulate matter was collected on 37mm diameter
of cooling of the ground. When these phenomena Teflon filters (Pall Flex) [24] by a gravimetric method
coexist, the conditions became favorable to accumula- using a Dichotomous sampler (Sierra Andersen 244,
tion of pollution, and the levels of particulate matter Smyrna, GA). This method allows the collection of
parregularly exceed the daily standard by U.S. Environmen- ticle sizes smaller than 2.5μm (fine fraction), and in the
tal Protection Agency and World Health Organization range of 2.5–10μm (coarse fraction) with a bulk flow
-1
(WHO) [16,17]. Previous studies have provided evidence rate of 16 – 18 l min . This semiautomatic equipment is
that particulate pollution in Santiago increases the risk programmable for sampling periods of 24 hours, and it
of mortality [4,18,19] and morbidity [20,21]. The most allows the simultaneous collection of the two particulate
recent studies were also able to differentiate the health fractions. The samples were collected from 10:00 a.m. to
effects of specific elemental components of particles 10:00 a.m. the next day in autumn and winter, and from
[18,22]. Unfortunately, as in the U.S., PM mass com- midnight to midnight in spring and summer. The2.5
ponents in Chile are not measured on a daily basis, measurements were performed daily from April to
hence the data are sparse, and time series analyses have September, every two days in October, November and
weak statistical power. March, and every three days in December, January and
We have previously introduced a methodology to take February from 1998 to 2007. The frequency of monitoring
better advantage of sparse data, specifically when speci- isbasedonthelevelsofpollutionobservedduring theyear
ation data only exist every 3-6 days. PM is monitored and decided by the National Environment Commission.2.5
more frequently, almost daily. The method was applied Therefore, daily monitoring in the cold months (April to
to U.S. mortality and morbidity data by Franklin et al. September) is consistent with higher levels of pollution.
[9] and Zanobetti et al. [11]. In this method, the first Lower pollutant concentrations have been observed in the
stage was fitted on a daily time series analysis by season warm season due to better ventilation conditions and
using daily PM data. In the second stage, we look at thereforeless frequent samplingwas performed.2.5
how the relative fraction of PM , from different ele- The physical conditioning of the filters was performed2.5
ments averaged by season, modifies the PM associ- in the gravimetric laboratory at the Department of Pub-2.5
ation. This same approach was subsequently adopted by lic Health of the Ministry of Health. Filters were weighted
Bell et al. [10]. In this study we have chosen a similar ap- before and after use on an electronic microbalance,
Preproach where we let the PM coefficients vary by cisa (Swiss) 40SM-200A, allowing 1μg error, and stored2.5
month, and used the monthly ratios of components to in individual plastic boxes in dry chambers. The
laboratotal mass to explain the variations in those coefficients. tory atmosphere had a 50% controlled relative humidity
We applied this approach to cause-specific mortality and temperature between 20°C and 25°C. The elemental
during the years 1998-2007. We extracted several differ- analyses for the PM filters were conducted using X-ray2.5
ent elements of fine particles (aluminium (Al), sodium fluorescence at the Desert Research Institute. Six to eight
(Na), silicon (Si), sulfur (S), chloride (Cl), calcium (Ca), filters per month were analyzed for elements, and
apchromium (Cr), manganese (Mn), nickel (Ni), potassium proximately 10% of the samples were blank. The limit of
(K), iron (Fe), copper (Cu), zinc (Zn), selenium (Se), detection (LOD) was calculated for each element as three
bromine (Br), lead (Pb)), and studied the associations times the standard error of the blanks. Only elements
with mortality for all cardiovascular (CVD), all respira- that had at least 95% of all reported values above LOD
tory, cerebrovascular, and chronic obstructive pulmonary were included in the statistical analysis, as previously