Monitoring personal, indoor, and outdoor exposures to metals in airborne particulate matter: Risk of contamination during sampling, handling and analysis

doi:10.1016/j.atmosenv.2007.03.018

Atmospheric Environment

Volume 41, Issue 28, September 2007, Pages 5897-5907

https://doi.org/10.1016/j.atmosenv.2007.03.018 Get rights and content

Abstract

Rigorous sampling and quality assurance protocols are required for the reliable measurement of personal, indoor and outdoor exposures to metals in fine particulate matter (PM_2.5). Testing of five co-located replicate air samplers assisted in identifying and quantifying sources of contamination of filters in the laboratory and in the field. A field pilot study was conducted in Windsor, Ont., Canada to ascertain the actual range of metal content that may be obtained on filter samples using low-flow (4 L min⁻¹) 24-h monitoring of personal, indoor and outdoor air. Laboratory filter blanks and NIST certified reference materials were used to assess contamination, instrument performance, accuracy and precision of the metals determination. The results show that there is a high risk of introducing metal contamination during all stages of sampling, handling and analysis, and that sources and magnitude of contamination vary widely from element to element. Due to the very small particle masses collected on low-flow 24-h filter samples (median 0.107 mg for a sample volume of approximately 6 m³) the contribution of metals from contamination commonly exceeds the content of the airborne particles being sampled. Thus, the use of field blanks to ascertain the magnitude and variability of contamination is critical to determine whether or not a given element should be reported. The results of this study were incorporated into standard operating procedures for a large multiyear personal, indoor and outdoor air monitoring campaign in Windsor.

Introduction

There is a growing need for accurate, representative data on daily exposures of urban populations to metal concentrations in airborne particulate matter. Metals present in particulate matter have been implicated in a variety of cardio-respiratory illnesses associated with exposure to urban air pollution in recent epidemiology studies (Burnett et al., 2000; Claiborn et al., 2002); animal models (Costa and Dreher, 1997; Vincent et al., 2001) and studies involving human volunteers (Sorensen et al., 2005). Transition metals (e.g., Mn, Cr, Cu, Ni, and Zn) receive particular emphasis due to linkages between oxidative stress and impaired lung function (Osonio-Vargas et al., 2003).

The present research was undertaken to develop standard operating procedures (SOPs) in preparation for a series of biannual personal exposure monitoring campaigns in Windsor, Ont., Canada under the Canada–US Border Air Quality Strategy. The city of Windsor is impacted by local and transboundary industrial emissions and vehicle exhaust (Diamond and Parker, 2004; Gilbertson and Brophy, 2001). These monitoring campaigns are designed to assess daily levels of exposure of Windsor residents, through inhalation of personal air, indoor air at their residence, and outdoor air at their residence, to transition metals in airborne particulate matter (including Ni, Zn, Cr, Mn and Cd) and other elements such as Pb and As arising from industrial and traffic sources.

Refined high-resolution approaches to exposure assessment, involving 24-h sampling of personal and indoor residential air in addition to outdoor air, use quiet low-flow samplers (Demokritou et al., 2001). Low-flow samplers typically operate between 2 and 10 L min⁻¹ to minimize noise and disruption while the participants are carrying out their normal daily routines. X-ray fluorescence (XRF) has been the traditional detection method used for multielement determination of air filter samples, where adequate particle masses (>1 mg) are obtained using dichotomous samplers (15–20 L min⁻¹) or high volume ambient air samplers (1000 L min⁻¹ or higher). However, particle masses obtained using low-flow air samplers may fall short of the mass requirements for quantitative XRF determination, and in such cases inductively coupled plasma mass spectrometry (ICP-MS) may be an appropriate choice (Rasmussen, 2004). Previously we have observed that ICP-MS was better-suited than XRF for trace and ultratrace metal analysis of residential air samples: out of 60 7-day (40 m³) low-flow air samples collected in Ottawa, Ont., only 29% were above XRF detection limits for Pb; 8% for Ni; and 3% for Cd (Rasmussen et al., 2006). Similarly, Schauer et al. (2006) found that while XRF instrumentation is well suited for the quantification of several major and minor light elements, the low detection limits of ICP-MS instrumentation are necessary for determination of heavier trace and ultratrace elements collected on low-flow 24-h filter samples.

Thus, the improved sensitivity and lower detection limits associated with ICP-MS make this method a suitable alternative to XRF for the goals of the present study. The specific objectives are to (1) identify and quantify sources of filter contamination during sampling, handling and analytical steps, (2) determine the relative contribution of metals arising from inadvertent contamination of filters compared to metals arising from the airborne particulate matter being sampled, and (3) recommend SOPs to minimize or, if possible, eliminate inadvertent sources of metal contamination.

The first stage of the experimental method consisted of a series of laboratory tests of the equipment and processes to be used for field monitoring in Windsor. The laboratory study was used to isolate potential contamination associated with the sampler (R&P ChemPass™) and pump (BGI 400 Sampling Pump) system to be deployed in the field. A separate test for contamination was performed on blank filters subjected to smoke stain reflectometry measurements. This component of the study, including sample digestion and multielement determination, was completed at Health Canada laboratories.

The second stage consisted of a pilot field study conducted in Windsor in which personal, indoor and outdoor PM_2.5 samples were collected. The pilot study represented the beginning of a multiyear monitoring program in the Windsor area, for which thousands of samples were to be collected. Therefore, at the pilot stage, it was important to identify a suitably equipped private laboratory with the capacity to process high volumes of samples according to SOPs that would be implemented consistently throughout the duration of the full study. Thus, all pilot study samples were analyzed by the private lab (Alberta Research Council), which provided an early opportunity to identify potential sources of contamination associated with sample preparation and analysis. This included contamination associated with gravimetric measurements, blank filters taken directly from the packages, and field blanks.

Section snippets

Mass measurement of PM_2.5

Pre- and post-mass measurements of PM_2.5 filter samples were performed at Health Canada's buoyancy-corrected gravimetric analysis facility (Archimedes M3™ patent pending; Rasmussen et al., 2005) for both laboratory and pilot field studies. The PFTE filters (Teflo™ with ring support; diameter 37 mm; pore size 2 μm) were pre-conditioned for 24 h inside a custom-designed chamber with automated controls to maintain environmental conditions at a constant air temperature of 21 °C (±0.5 °C) and constant

Results and discussion

The low-flow (4 L min⁻¹) personal and stationary residential air samplers that were used in this study yielded very low total air volumes (∼6 m³) over the 24-h sampling period. The resulting air filter samples contained very small particle masses (median 0.107 mg). To realize the benefits of improved sensitivity and lower detection limits that are associated with ICP-MS, it was necessary to first identify and quantify all possible sources of contamination during sample handling and processing.

Summary and conclusions

As ICP-MS instrumentation is introduced into a sampling milieu which has been dominated by XRF, the improved sensitivity and lower detection limits associated with ICP-MS must be accompanied by increased rigor in filter sample handling and processing, to avoid inadvertent contamination which impacts the reliability of the ICP-MS determinations. In this study, sources of filter contamination during personal air monitoring campaigns were assessed, and critical steps were identified to minimize

Acknowledgments

Sincere thanks go to the Windsor participants for their cooperation and efforts, to Iris Xu, staff and students at University of Windsor for conducting the field pilot sampling, and to H. David Gardner, Keith Van Ryswyck and Ryan Kulka for their assistance throughout the study. We express our appreciation to Owen Butler and Sam Wunderli for valuable advice and inspiration at the outset of the study. The authors gratefully acknowledge funding from Health Canada Safe Environments Program (Border

References (22)

R.T. Burnett et al.
Association between particulate and gas-phase components of urban air pollution and daily mortality in eight Canadian cities
Inhalation Toxicology
(2000)
CEN, 2005. EN14902 Ambient Air Quality. Standard method for the measurement of Pb, Cd, As and Ni in the PM10 fraction...
C.S. Claiborn et al.
Testing the metals hypothesis in Spokane, Washington
Environmental Health Perspectives
(2002)
D.L. Costa et al.
Bioavailable transition metals in particulate matter mediate cardiopulmonary injury in healthy and compromised animal models
Environmental Health Perspectives
(1997)
P. Demokritou et al.
Development and laboratory performance evaluation of a personal multipollutant sampler for simultaneous measurements of particulate and gaseous pollutants
Aerosol Science and Technology
(2001)
G. Diamond et al.
Preliminary Air Quality Assessment Related to Traffic Congestion at Windsor's Ambassador Bridge
(2004)
M. Gilbertson et al.
Community health profile of Windsor. Ontario, Canada: anatomy of a Great Lakes area of concern
Environmental Health Perspectives
(2001)
L.M. Jalkanen et al.
Simple method for the dissolution of atmospheric aerosol samples by inductively coupled plasma mass spectrometry
Journal of Analytical Atomic Spectrometry
(1996)
K.J. Koistinen et al.
Fine particle (PM2.5) measurement methodology, quality assurance procedures, and pilot results of the EXPOLIS study
Journal of the Air and Waste Management Association
(1999)
P.A. Lawless et al.
Maximizing data quality in the gravimetric analysis of personal exposure sample filters
Journal of the Air and Waste Management Association
(1999)

K.R. Lum et al.

The potential availability of P, Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn in urban particulate matter

Environmental Technology (Letters)

(1982)

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Monitoring personal, indoor, and outdoor exposures to metals in airborne particulate matter: Risk of contamination during sampling, handling and analysis

Abstract

Introduction

Section snippets

Mass measurement of PM2.5

Results and discussion

Summary and conclusions

Acknowledgments

Association between particulate and gas-phase components of urban air pollution and daily mortality in eight Canadian cities

Inhalation Toxicology

Testing the metals hypothesis in Spokane, Washington

Environmental Health Perspectives

Bioavailable transition metals in particulate matter mediate cardiopulmonary injury in healthy and compromised animal models

Environmental Health Perspectives

Development and laboratory performance evaluation of a personal multipollutant sampler for simultaneous measurements of particulate and gaseous pollutants

Aerosol Science and Technology

Preliminary Air Quality Assessment Related to Traffic Congestion at Windsor's Ambassador Bridge

Community health profile of Windsor. Ontario, Canada: anatomy of a Great Lakes area of concern

Environmental Health Perspectives

Simple method for the dissolution of atmospheric aerosol samples by inductively coupled plasma mass spectrometry

Journal of Analytical Atomic Spectrometry

Fine particle (PM2.5) measurement methodology, quality assurance procedures, and pilot results of the EXPOLIS study

Journal of the Air and Waste Management Association

Maximizing data quality in the gravimetric analysis of personal exposure sample filters

Journal of the Air and Waste Management Association

The potential availability of P, Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn in urban particulate matter

Environmental Technology (Letters)

Mass measurement of PM_2.5