Exposure Assessment

The overall goal of the Exposure Assessment Facility Core is to enhance the research capabilities of Center investigators by providing expertise in a number of related activities and services not available elsewhere in the University, including exposure assessment design, methods development, sampling and analysis. The Facility Core is composed of three analytical laboratories with distinct capabilities, as well as expertise in study design and exposure assessment techniques, and a wide array of sampling equipment. The laboratories are located at the Mailman School of Public Health Campus (MSPH) in NYC and at the Lamont-Doherty Earth Observatory (LDEO) Campus. The three analytical laboratories include the Environmental Geochemistry Laboratory (LDEO), the Trace Organics Laboratory (LDEO) and the Allergen Laboratory (MSPH).

This Facility Core supports the development and implementation of exposure assessments by coordinating the following services and activities:

  • Study design, methods development, design and development of new sampling equipment, air and settled dust sampling, and analysis of samples;

  • Expansion of these facilities and efforts in ways that support the evolving strategic goals of the CEHNM;

  • Training and mentoring of staff, students, fellows and researchers;

  • Responding to exposure emergencies;

  • Responding to the needs of the Community Outreach and Engagement Core (COEC) and local community organizations in a number of ways, including testifying in public hearings and carrying out pilot field work to test whether perceived sources of air pollution exist and can be documented. 

Core Director:  
chilli [at] ldeo.columbia.edu (Steven Chillrud), PhD (LDEO)

Environmental Geochemistry Lab Leader: 
chilli [at] ldeo.columbia.edu (Steven Chillrud), PhD (LDEO)

Allergen Lab Leader: 
mp2217 [at] columbia.edu (Matthew Perzanowski), PhD (MSPH/EHS)

Trace Organics Lab Leader: 
yanbz [at] ldeo.columbia.edu (Beizhan Yan), PhD (LDEO)

Exposure Assessment Design Leader: 
plk3 [at] columbia.edu (Patrick Kinney), ScD (MSPH/EHS)

Environmental Geochemistry: jmr79 [at] columbia.edu (James Ross), MS (LDEO)
Allergen: ad708 [at] columbia.edu (Adnan Divjan) (MSPH/EHS)
Trace Organics: mp2832 [at] columbia.edu (Masha Pitiranggon), BA (LDEO)

Core Service Costs

Description of Services

Exposure Assessment Study Design

Interested parties meet with one of the Exposure Core leaders. For studies involving sample collection, information is provided to the investigator recommending appropriate methods for sample collection and processing for the proposed assays.  Decisions are made, in consultation with the investigator, regarding the numbers and types of samples to be collected (e.g., short- or long-term monitoring; personal, indoor, outdoor; integrated vs. real-time; chemical characterization, etc.). The appropriate lab leader advises the investigator about the strengths and limitations of alternative sampling and analysis methods, measurement error issues and the recommended study design. Once a design has been established, the Core assesses the approximate number and timing of sample collection and processing, to be certain that the Facility can handle the workload. 

Equipment Loans for Sampling and Monitoring Equipment

Pilot projects can borrow equipment if not in use for other projects.  The Exposure Core currently has the ability to collect integrated personal and area air samples for analysis of Total Suspended Particulates (TSP), PM10, PM2.5, black carbon, PAHs, airborne allergens and a long list of particle-associated metals and elements. The Core also samples for dustborne allergens using vacuum methods. The equipment includes both personal size battery operated pumps (twelve BGI 400S pumps that can be set at fixed flows ranging from 0.5 to 4 LPM, five SKC pumps that operate at 1 LPM, five customized occupational holster pumps that operate at 4 LPM), to pumps made to operate off of line power (five multi-pump sampling boxes that operate from 1 – 4 LPM, one Dicot monitor that operates at 28 LPM, and one high volume TSP sampler that operates at 1000 LPM).  Capabilities for real-time area sampling include particle counts between 0.3 and 5 μm aerodynamic diameter (with two Met-One 237B particle counters and 1 Met-One 7350 particle counter), two ozone monitors (Thermo Anderson and Tech2B), five rack-mounted aethalometers (Magee Scientific) and a Met-One Beta Attenuation Monitor for PM2.5 monitoring (though it is in need of a major upgrade to take care of systematic errors). Real-time personal monitoring equipment includes two PDR-1200, ten microAeths, 13 microPEMS, and ten PAS7000 CO monitors (Draeger). We also have a number of primary and secondary flow meters including a Buck bubble meter, two TSI mass flow meters and a low flow Altech mass flow meter in addition to a number of rotometers. Pneumatic traffic counters are also available.

Design and Development of New Sampling Equipment and Maintenance of Current Field Equipment

For studies with sampling needs that cannot be met by currently available equipment, the Exposure Core facilities at LDEO are able to design and manufacture customized sampling equipment. This work has been led by Tom Protus, a senior electrical engineer, who has packaged off-the-shelf components into integrated, customized sampling equipment for a wide variety of Center-supported pilots and projects over many years. Examples include multi-pump home indoor and outdoor air sampling equipment, personal monitors for a pilot on subway occupational exposures, and adding sound dampening enclosures and automatic timers for existing indoor air monitors. For more sophisticated design and manufacturing needs (e.g., microelectronic, processor-controlled monitoring systems), the LDEO Instrument Development Facility and outside vendors are used. 

Laboratory Analysis of Samples

Processing and storage of samples

The Exposure Core provides multiple bar code labels for field logs as well as labeling of the sample holders such as filter cassettes and filter petri dishes. This allows for accurate and efficient tracking of samples both in the field and the laboratory. Samples can be dried, ground or sealed in airtight cans and can be stored at room temperature, refrigerated (at 4°C) or frozen (both at -15°C and -80°C).  Samples can also be stored at special temperatures under nitrogen or under glycol to preserve oxidation states. For shipping, processing and analysis of environmental samples collected in foreign countries, the Exposure Core has recently adopted procedures to comply with new, stricter requirements of the US Department of Agriculture which requires a permit for importing filters of airborne particulate matter.

Environmental Geochemistry Laboratory (LDEO): Filters

A large fraction of the services are related to processing and analysis of filters of airborne particulate matter, including purchasing, preparation, archiving and laboratory analysis of the filters.  Pre- and post-weighing of filters: filters are weighed after a minimum of 24 hours of conditioning in our HEPA-filtered, environmentally controlled weighing glove box (controlled to 40±2% RH and 72±2°F) on a Metler Toledo UMX2 microbalance. Other non-destructive analyses of filters include optical reflectance methods (to determine black carbon and the amount of different UV-active particulate matter sources such as cigarette smoke, wood smoke or very high concentrations of iron oxides)2 and polarized energy dispersive X-ray fluorescence spectroscopy (to determine a wide suite of elemental concentrations from Na to Pb).  Custom calibrations have been carried out for both filters (16 elements) and powdered aquifer sands (4 elements, As, Fe, Mn, Al).

Sample preparation and trace element analysis by ICP-MS

Environmental samples (including water samples and other solutions, PM filters and sediments, acidified water samples and microwave or open beaker digests of particulate matter samples) can be analyzed by magnetic sector, high resolution ICP-MS for a wide array of elements with detection limits orders of magnitude lower than XRF.4,5  Our standard protocol measures 28 elements from Na to Pb.  Specialized preparation allows analysis of platinum group elements (Pt, Pd, Rh) on small mass filters and particulate matter samples.6  Testing of 40 micron-scale spatial heterogeneities in elemental composition of solids can be carried out on the laser ablation ICP-MS. Finally, the Exposure Core also has a method for analyzing Pb isotope ratios by multi-collector ICP-MS for environmental samples and blood.7,8

Allergen Laboratory (MSPH)

The allergen lab provides sampling, extraction and analytical capabilities for measuring allergens in dust and airborne particulate matter samples, including Bla g 1, Bla g 2, Mus m 1, MUP, Fel d 1, Can f 1, Der f 1, Der p 1, and Blo t 5. In response to community concerns about bed bugs, we expanded our services and developed two novel immunoassays to bed bug allergens in order to determine the prevalence of sensitization to bed bug allergens among adults with a report of bed bug bites. We successfully developed assays for measuring IgE antibodies to both crude C. lectularius and cNP, a unique protein from C. lectularius. We also have the capability of measuring IgE to most inhalent and food allergens through the ThermoFisher CAP system.  We provide sampling equipment for single- and multi-flow exhaled NO and exhaled breath condensate. 

Trace Organics Laboratory (LDEO)

This lab provides sample preparation, extraction and analytical support for measurement of a wide array of trace organics including PAH, hydroxyl- and oxygen-containing PAHs, oxidative stress and inflammation biomarkers and other analytes by GC/MS/MS, 2DGC, and LC/MS/MS.

Method development

One of the strengths of the Exposure Core is its ability to develop or learn new methods in support of new initiatives, pilot projects and inter-center collaborations. Examples include sampling and analysis methods for airborne cockroach allergens,9 a negative chemical ionization GC/MS/MS method for oxygenated PAHs, the LC-MS/MS methods being used for quantifying exhaled breath condensate samples for markers of inflammation, oxidative stress and dilution (8-isoprostanes and urea), the analysis of airborne particulate matter filters of black carbon and second hand smoke,2 and the analysis of airborne particulate matter for platinum group elements (Pt, Rd, Rh).6  Realizing the carcinogenic and mutagenic nature of oxygenated PAHs and their high abundance in urban air, the Exposure Core began to develop methods for analyzing this important class of compounds in 2010 and 2011, paying special attention to those compounds transformed from parental PAHs in air.

Quality Control Assurance

QC is the essence of the analytical facilities that form the basis of the Exposure Core.  As an overview, the Core relies on standard procedures for investigating blanks (instrument blanks, procedural blanks and field blanks) and preparing standard calibration curves. It runs a wide range of standard reference materials (SRMs) and internal standards to track recovery and reproducibility for each analyte of interest. The standards are run for the different matrices analyzed and include: filters of airborne particulate matter of different aerodynamic diameter (PM2.5, PM10, etc.), dust samples, soil samples, water samples and exhaled breath condensate. For all analyses, sample data must successfully meet acceptance criteria based on QA/QC samples or they will be flagged and/or not used. For samples run by HR-ICP-MS, instrumental performance and blank levels are assessed at the beginning of the day. These criteria must be acceptable in order to run unknown samples. Calibration curves are made from stock solutions tested and compared against independent NIST SRMs as well as other inter-laboratory certified standards and an in-house consistency standard. For both trace and major element analysis, stock calibration standards are mixed with internal standard solutions to generate a straight line calibration curve that fully encompasses the general known range of the elemental concentrations in samples from the various study areas. QC samples, including reference materials, are also run interspersed among unknown samples. For the work done by HPLC-ICP-MS, the same approach is used. XRF analyses of solid samples includes running blanks and SRMs as well as generating matrix specific calibrations based on comparison to samples digested and run by ICP-MS or analysis of SRMs. In addition, with each batch of unknowns, a blank and an internal standard are run on the XRF spectrometer. 

For allergen analyses, serial dilution standard curves are run on every ELISA and multiplex microtitre plate. In addition, for allergens critical to a study (e.g., mouse allergen in the mouse allergen intervention trial) an additional QC sample is included on all plates. For the LC/MS/MS analysis of exhaled breath condensate (EBC) samples, QA/QC control is implemented throughout the analysis of 8-isoprostane and urea. Known levels of stable isotope-labeled internal standard (8-iso-D4 and urea-2N15) are added to correct for potential loss of analytes during the purification and concentration steps prior to instrument analysis. The calibration standards are measured at the beginning of each batch of samples and if results are not within acceptable levels for linearity and blanks, then samples are not run until the problem is identified and rectified. If this fails, the LC/MS/MS is cleaned and/or serviced.  During a batch of analyses, one of the internal standards is injected at the beginning and after every ten unknowns (samples) to monitor for instrument drift and precision. Two standards, which represent the low and high ends of biomarker levels in EBC, are run after approximately every 15th unknown sample in the same batch. Finally at the end of a batch, a final standard is run. If QC results are not within assigned values, results are flagged or rejected depending on the size of the error and a progressive diagnosis procedure is started to evaluate possible cause(s).