Christopher D Simpson

Christopher D Simpson
University of Washington Seattle | UW · Department of Environmental and Occupational Health Sciences

MS, PhD

About

112
Publications
13,085
Reads
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4,489
Citations
Citations since 2016
39 Research Items
2436 Citations
20162017201820192020202120220100200300
20162017201820192020202120220100200300
20162017201820192020202120220100200300
20162017201820192020202120220100200300
Additional affiliations
January 2012 - present
January 2011 - present
Asian Institute of Technology
January 2007 - present

Publications

Publications (112)
Article
Wildland firefighters (WLFFs) are exposed to a mixture of chemicals found in wildland fire smoke and emissions from nonwildland-fuel smoke sources such as diesel. We investigated compositional differences in exposure to particulate matter and explored differences in ventilation rate and potential inhaled dose relative to the work tasks of WLFFs. Re...
Article
α-Diketones such as diacetyl (2,3-butanedione) and 2,3-pentanedione are generated during the roasting and fermentation of foods and are also used as flavoring compounds. Exposure to these compounds has been associated with obliterative bronchiolitis in popcorn and coffee manufacturing workers. This study found concentration excursions were higher i...
Article
Full-text available
Objectives: Despite the widespread use of manganese (Mn) in industrial settings and its association with adverse neurological outcomes, a validated and reliable biomarker for Mn exposure is still elusive. Here, we utilize targeted metabolomics to investigate metabolic differences between Mn-exposed and -unexposed workers, which could inform a putat...
Article
Background: Alpha-diketones such as diacetyl and 2,3-pentanedione have been used as artificial flavorings in a variety of industries and are produced naturally when food products such as coffee beans are roasted. Exposure to these compounds has been associated with bronchiolitis obliterans, a rare and severe respiratory disease. In the current pap...
Article
This study utilized laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to quantify gadolinium in the hair of autopsy cases that had received gadolinium-based contrast agents (GBCAs) before death. Consecutive autopsy cases were reviewed for GBCA injections and subjects who received a single type of GBCA in the year before death...
Article
Legal commercial cultivation and processing of cannabis is a rapidly growing industry in multiple countries. However, to date little effort has been made to characterize and identify the various occupational hazards that workers may be facing in the cannabis production industry, including airborne contaminants that may affect the human respiratory...
Article
Background: While little is known about the occupational hazards associated with Cannabis cultivation, both historical research in the hemp industry and preliminary data from modern grow houses, suggest that Cannabis workers may be at increased risk of respiratory and allergic diseases. Objectives: We sought to investigate the association betwee...
Article
Objectives: We used laser ablation inductively coupled plasma mass spectrometry to quantify gadolinium in hair samples from autopsy cases with gadolinium-based contrast agent (GBCA) exposure. Hair gadolinium data were correlated with gadolinium concentrations in brain, skin, and bone tissues from the same case to investigate a potential noninvasiv...
Article
The absolute principal component scores (APCS) model was applied to on-road, background-adjusted measurements of NOx, CO, CO2, black carbon (BC), and particle number (PN) obtained from a continuously moving platform deployed during 16 afternoon sampling periods in Los Angeles, CA. High-emitter biasing observations were separated from the vehicle fl...
Article
Objectives: The legalization of the production, sale, and possession of cannabis in Washington State in 2012 not only created the framework for a new legal industry, but also for a new regulated labor sector. In addition to typical occupational health and safety hazards associated with chemical and physical exposures, the transition from an illici...
Article
Emerging nanomaterials like nanozymes have recently been applied for the immunoassay-based detection of biomarkers. However, the inferior catalytic activity and low water solubility of nanozymes remain as the major limitations compared to natural enzymes. To overcome these limitations, we successfully synthesized a superior nanozyme with a structur...
Article
Background: Untargeted metabolomics analysis is a valuable tool in the field of metabolic profiling of biological samples, but it has been less widely applied to characterization of environmental mixtures. The current study explores using untargeted analysis of environmental samples of air pollution for component analysis and source appointment. Me...
Article
Full-text available
Background: Wildland firefighters conducting prescribed burns are exposed to a complex mixture of pollutants, requiring an integrated measure of exposure. Objective: We used urinary mutagenicity to assess if systemic exposure to mutagens is higher in firefighters after working at prescribed burns versus after non-burn work days. Other biomarkers of...
Article
In this work, we present an ultra-low-cost smartphone device for in situ quantification of OP poisoning severity. The performance of the lens-less smartphone spectrum apparatus (LeSSA) is evaluated using standard human Interleukin-6 (IL-6) immunoassay kits. Upon dose-response curve fitting, LeSSA demonstrates an accuracy of 99.5%. The limit of dete...
Chapter
Diesel engine emissions are rich in PAHs and NPAHs, and vehicular emissions are a major source of PAHs and NPAHs in urban air. Specific NPAHs, including 1-nitropyrene, are enriched in diesel exhaust relative to other sources and have been used as source-specific tracers for diesel exhaust. However, changes in diesel engines and emission control tec...
Article
Mobile monitoring and passive sampling device (PSD) monitoring are popular air pollutant measurement techniques with complementary strengths and weaknesses. This study investigates the utility of combining data from concurrent two-week mobile monitoring and PSD campaigns in Los Angeles in summer and early spring to identify sources of traffic-relat...
Article
Air pollution exposure and HIV infection can each cause neurocognitive insult in children. The purpose of this study was to test whether children with combined high air pollution exposure and perinatal HIV infection have even greater risk of neurocognitive impairment. This was a cross-sectional study of HIV-uninfected unexposed (HUU) and HIV-infect...
Article
Full-text available
We investigated the viability of particle bound 1-nitropyrene (1-NP) air concentration measurements as a surrogate of diesel exhaust (DE) exposure, as compared with industry-standard elemental carbon (EC) and total carbon (TC) measurements. Personal exposures are reported for 18 employees at a large underground metal mine during four different moni...
Article
A novel sandwich immunoassay based immunochromatographic test strip (ICTS) has been developed for simultaneously measuring both butyrylcholinesterase (BChE) activity and the total amount of BChE (including inhibited and active enzyme) from 70 μLpost-exposure human plasma sample. The principle of this method is based on the BChE monoclonal antibody...
Conference Paper
Manganese (Mn) is a known neurotoxicant, and given its health effects and ubiquitous nature in metal-working settings, identification of a valid and reproducible biomarker of exposure is of interest. Global metabolomics were previously utilised to determine metabolites that differ between occupational groups defined by Mn exposure status, in hopes...
Article
Objectives: Examine associations between pesticide exposure and signs or symptoms of parkinsonism. Methods: Prior to the 2014 pesticide spray season we examined 38 active pesticide handlers age 35-65 (median 43.5) who participated in the State of Washington's cholinesterase monitoring program in the Yakima Valley, where cholinesterase-inhibiting...
Article
Full-text available
This article is being retracted at the request of the authors because of inadvertent errors in the statistical code that resulted in the exclusion of 12 gestational diabetes mellitus cases with urinary cadmium below the limit of detection. The coding errors do not impact any other published studies of this population. In Table 1, the corrected geom...
Article
Objectives: Manganese (Mn) is a known neurotoxicant, and given its health effects and ubiquitous nature in metal-working settings, identification of a valid and reproducible biomarker of Mn exposure is of interest. Here, global metabolomics is utilized to determine metabolites that differ between groups defined by Mn exposure status, with the goal...
Article
We have applied the absolute principal component scores (APCS) receptor model to on-road, background-adjusted measurements of NOx, CO, CO2, black carbon (BC), and particle number (PN) obtained from a continuously moving platform deployed over nine afternoon sampling periods in Seattle, WA. Two Varimax-rotated principal component features described...
Article
Salmon exposed to waterborne metals can experience olfactory impairment leading to disrupted chemosensation. In the current study, we investigated the effects of cadmium (Cd) on salmon olfactory function by modeling an exposure scenario where juvenile salmon transiently migrate through a polluted waterway. Coho were exposed to environmentally-relev...
Article
Metabolomics is an analysis technique used to characterise the set of small-molecule metabolites found in a biofluid, and has commonly been used to investigate biochemical differences between diseased and non-diseased groups. Limited research has looked at how metabolomics profiles differ in occupationally exposed and unexposed groups, and what the...
Article
The assessment of occupational exposure to diesel exhaust (DE) is of interest from an epidemiological perspective. Urinary biomarkers of exposure have been proposed as a potential novel approach for measuring exposure to DE. In this study, we measured the concentrations of two urinary metabolites of 1-nitropyrene (1NP), a nitrated polycyclic aromat...
Article
Chemicals are an integral component of laboratory activities in academia but minimizing hazards and environmental impacts of chemicals is challenging. This paper describes how laboratories in University of Washington’s Department of Environmental and Occupational Health Sciences (UW DEOHS) partnered with the UW Green Laboratory Program to explore a...
Article
Full-text available
Purpose: We sought to understand the time course between exposure to manganese (Mn) and uptake into the blood, to allow a more meaningful interpretation of exposure biomarker data, and to determine the utility of blood as a biomarker of Mn exposure. Methods: Welder trainees were monitored over the course of a five-quarter training program. Each...
Article
Full-text available
Increasing evidence suggests an inverse association between cadmium (Cd) and size at birth, potentially greatest among female neonates. We evaluated whether greater maternal body burden of Cd is associated with reduced neonatal anthropometry (birthweight, birth length, head circumference, and ponderal index) and assessed whether these associations...
Article
Full-text available
Air pollution exposure prediction models can make use of many types of air monitoring data. Fixed location passive samples typically measure concentrations averaged over several days to weeks. Mobile monitoring data can generate near continuous concentration measurements. It is not known whether mobile monitoring data are suitable for generating we...
Article
Mobile monitoring has provided a means for broad spatial measurements of air pollutants that are otherwise impractical to measure with multiple fixed site sampling strategies. However, the larger the mobile monitoring route the less temporally dense measurements become, which may limit the usefulness of short-term mobile monitoring for applications...
Article
Diesel exhaust presents a community exposure hazard, but methods to measure internal exposure are lacking. We report results from a community-based study using 1-nitropyrene (1-NP) and its urinary metabolites as markers of exposure to traffic-related diesel particulate matter (DPM). The study participants were Tijuana, Mexico residents who commuted...
Article
Wildland firefighter's exposure to wildland fire or vegetative biomass smoke has mostly been assessed by personal monitoring to airborne pollutants. However, the use of biomarkers may accurately reflect the internal (systemic) dose received by the firefighter. In this study, we assessed occupational exposure to wildland fire smoke in 14 wildland fi...
Article
Full-text available
This article presents a new methodology to potentially quantify polycyclic aromatic hydrocarbon (PAH) isomers using high-resolution time of flight aerosol mass spectrometer (HR-AMS). The fragmentation of PAHs within the HR-AMS is such that significant signal remains at the molecular ion. After quantifying the molecular ion signal and taking into ac...
Article
With emerging evidence that diesel exhaust exposure poses distinct risks to human health, the need for fine-scale models of diesel exhaust pollutants is growing. We modeled the spatial distribution of several nitrated polycyclic aromatic hydrocarbons (NPAHs) to identify fine-scale gradients in diesel exhaust pollution in two Seattle, WA neighborhoo...
Article
Epidemiologic studies have linked diesel exhaust (DE) to cardiovascular and respiratory morbidity and mortality, as well as lung cancer. DE composition is known to vary with many factors, although it is unclear how this influences toxicity. We generated eight DE atmospheres by applying a 2 × 2 × 2 factorial design and altering three parameters in a...
Article
Full-text available
Quantifying exposure and dose to manganese (Mn) containing airborne particles in welding fume presents many challenges. Common biological markers such as Mn in blood or Mn in urine have not proven to be practical biomarkers even in studies where positive associations were observed. However, hair Mn (MnH) as a biomarker has the advantage over blood...
Article
Rice straw (RS) field burning, commonly practiced in Asia, produces large amounts of toxic air pollutants but has not been comprehensively characterized. This study conducted field and laboratory measurements for gaseous pollutants and semi-VOCs (16 PAHs, 16 chlorinated pesticides and 14 PCBs) in RS burning smoke to determine emission factors (EFs)...
Article
Manganese (Mn) exposure is associated with increased T1-weighted Magnetic Resonance Imaging (MRI) signal in the basal ganglia. T1 signal intensity has been correlated with occupational Mn exposure but not with clinical symptomatology or neuropathology. This study investigated predictors of ex-vivo T1 MRI basal ganglia signal intensity in neuropatho...
Article
Full-text available
Environmental cadmium (Cd) exposure is associated with type 2 diabetes. However, the association of Cd and gestational diabetes mellitus (GDM) is unknown. We examined the association between body burden of Cd and GDM risk. We used 140 GDM cases and 481 randomly selected non-case subcohort members from the Omega Study to conduct a case-cohort study....
Article
Woodsmoke contains harmful components - such as fine particulate matter (PM2.5) and polycyclic aromatic hydrocarbons (PAHs) - and impacts more than half of the global population. We investigated urinary hydroxylated PAH metabolites (OH-PAHs) as woodsmoke exposure biomarkers in nine non-smoking volunteers experimentally exposed to a wood fire. Indiv...
Article
A mobile monitoring platform developed at the University of Washington Center for Clean Air Research (CCAR) measured 10 pollutant metrics (10 s measurements at an average speed of 22 km/hr) in two neighborhoods bordering a major interstate in Albuquerque, NM, USA from April 18-24 2012. 5 days of data sharing a common downwind orientation with respe...
Article
Long-term, high-level exposure to manganese (Mn) is associated with impaired central nervous system (CNS) function. We quantitatively explored relations between low-level Mn exposure and selected neurological outcomes in a longitudinal inception cohort of asymptomatic welder trainees. Welders with no previous occupational Mn exposure were observed...
Article
Full-text available
Objectives: Organophosphate (OP) and N-methyl-carbamate (CB) insecticides are used widely in agriculture to manage insect pests of economic importance. Agricultural workers are more likely to suffer exposure because of the widespread use of OP/CBs in agriculture, and pesticide-related illnesses among handlers may be more severe when compared to oth...
Article
Full-text available
The objective of this study was to use membrane introduction mass spectrometry (MIMS), implemented on a mobile platform, in order to provide real-time, fine-scale, temporally and spatially resolved measurements of several hazardous air pollutants. This work is important because there is now substantial evidence that fine-scale spatial and temporal...
Article
Various biomarkers of exposure have been explored as a way to quantitatively estimate an internal dose of manganese (Mn) exposure, but given the tight regulation of Mn in the body, inter-individual variability in baseline Mn levels, and variability in timing between exposure and uptake into various biological tissues, identification of a valuable a...
Article
Full-text available
Despite evidence of adverse health effects resulting from exposure to manganese (Mn), biomarkers of exposure are poorly understood. To enhance understanding, mean blood Mn (MnB) and mean air Mn (MnA) were extracted from 63 exposure groups in 24 published papers, and the relationship was modeled using segmented regression. On a log/log scale, a posi...
Article
Full-text available
Epidemiologic and toxicologic studies were carried out in concert to provide complementary insights into the compositional features of ambient particulate matter (PM*) that produce cardiovascular effects. In the epidemiologic studies, we made use of cohort data from two ongoing studies--the Multi-Ethnic Study of Atherosclerosis (MESA) and the Women...
Article
Levoglucosan, a sugar anhydride and a combustion breakdown product of cellulose is a dominant organic constituent of particles in woodsmoke. After exposure, levoglucosan is excreted unmetabolized in urine. Urinary levoglucosan was assessed as a biomarker of occupational woodsmoke exposure among wildland firefighters. Urine samples were collected fr...
Article
Full-text available
Wildland firefighters are occupationally exposed to elevated levels of woodsmoke. Eighteen wildland firefighters were monitored for their personal exposure to particulate matter with median aerodynamic diameter of 2.5 microns (PM2.5), levoglucosan (LG), and carbon monoxide (CO) at 30 prescribed burns at the Savannah River Site, South Carolina. Line...
Article
Informal recycling is widespread in developing countries and involves the collection, sorting, and selling of recyclable materials. Workers are exposed to hazards including the risk of cuts and musculoskeletal injury, infection, exposure to medical waste, and respiratory conditions like bronchitis, pneumonia, and sinusitis and often use insufficien...
Article
Full-text available
Diesel exhaust (DE) is a significant contributor to the toxicity associated with particulate matter (PM). 1-Nitropyrene (1-NP) has been used as a molecular marker for DE, and the urinary metabolites of 1-NP have been proposed as biomarkers for exposure to DE. In this study, several urinary 1-NP metabolites were evaluated for their utility as marker...
Article
Public transport vehicle drivers, especially in highly polluted or trafficked areas, are exposed to high levels of air pollutants. In this study, we assessed the influence of traffic on levels of hydroxy polycyclic aromatic hydrocarbons (OH-PAHs) in commercial bus drivers in Trujillo, Peru, by measuring the within-shift changes in the urinary whole...
Conference Paper
Walk-in-line pedestrians crossing the U.S.-Mexico border northbound at the San Ysidro, CA Port of Entry may be at an increased risk from traffic-related pollution including elevated diesel particulate matter (DPM) exposure. DPM exposure has been associated with numerous adverse health effects, including respiratory problems and lung cancer. Pedestr...
Article
Biomass burning is one of the major sources of organic carbon aerosols. However, there is limited information on the temporal and spatial variability for the impact of biomass burning in most regions of the United States, including the upper Midwest. In an attempt to obtain information on these variabilities, high-performance anion-exchange chromat...
Article
Emission from field burning of crop residue, a common practice in many parts of the world today, has potential effects on air quality, atmosphere and climate. This study provides a comprehensive size and compositional characterization of particulate matter (PM) emission from rice straw (RS) burning using both in situ experiments (11 spread field bu...
Article
Full-text available
It has been clearly established that exposure to wood smoke is associated with a variety of adverse health effects in humans. However, we still have much to learn about the relationship between wood-smoke exposure and disease, including determination of what should be considered a "safe" level of exposure, and whether wood smoke should be regulated...
Article
Exposures to particulate matter (PM) of both 10-2.5 microm (PM(10-2.5)) and below 2.5 microm (PM(2.5)) were measured for a cohort of taxi drivers in Shenyang, China, during August 2007. PM samples were collected inside and outside the taxi during the drivers' workshifts, and also inside the drivers' homes when they were off-shift. Ambient PM sample...
Article
Full-text available
Urinary levoglucosan was investigated as a potential biomarker of wood smoke exposure in two different controlled experimental settings. Nine subjects were exposed to smoke from a campfire in a controlled setting, and four were exposed to smoke from an older-model wood stove. All subjects were asked to provide urine samples before and after exposur...
Article
Full-text available
This study focuses on comparing different measurements of biomass smoke exposure among "rice in the bamboo" producing workers in Thailand. Repeated measurements of PM2.5, levoglucosan, and urinary methoxyphenols concentrations from a subsample of the exposed workers were analyzed. The analyses of variance components and variance ratios were calcula...
Conference Paper
We have modified a quadrupole ion trap GC-MS/MS system for use as an on-line air monitoring platform for volatile and semi-volatile (VOC and SVOC) molecules using a capillary hollow fibre semi-permeable membrane introduction interface. Continuous on-line quantitation of target analytes is achieved using an in-line permeation tube for the continuous...
Article
Full-text available
Membrane introduction mass spectrometry (MIMS) is emerging as an important technique for on-line, real-time environmental monitoring. Because MIMS interfaces are simple and robust, they are ideally suited for operation in MS instrumentation used for in-field applications. We report the use of an on-line permeation tube to continuously infuse an iso...
Article
Full-text available
Urinary methoxyphenols (MPs) have been proposed as biomarkers of woodsmoke exposure. However, few field studies have been undertaken to evaluate the relationship between woodsmoke exposure and urinary MP concentrations. We conducted a pilot study at the US Forest Service-Savannah River Site, in which carbon monoxide (CO), levoglucosan (LG), and par...
Article
Fine particulate matter (PM(2.5)) is associated with respiratory effects, and asthmatic children are especially sensitive. Preliminary evidence suggests that combustion-derived particles play an important role. Our objective was to evaluate effect estimates from different PM(2.5) exposure metrics in relation to airway inflammation and lung function...
Article
Eastern Washington is compromised by various pollution sources, of which agricultural burning is a particular burden. Smoke from field burning is a nuisance to nearby communities and is a concern for health. This study evaluates levoglucosan (LG) and methoxyphenols (MPs) as potential tracers for apportioning field burning smoke. PM2.5 (particulate...
Article
1-Nitropyrene (1-NP) is enriched in diesel exhaust particulate matter (DPM) relative to other sources of particulate matter (PM), and has been proposed as a marker for DPM. However, in ambient air, 1-NP concentrations are typically in the low pg/m(3) range. Therefore, collection of large volume air samples coupled with extensive sample clean-up pro...
Article
1-nitropyrene (1-NP) is one of the most abundant nitrated polycyclic aromatic hydrocarbons (NPAHs) in diesel exhaust particulate matter (DEP) and is a main contributor of direct-acting mutagenicity in DEP. Therefore, the metabolites of 1-NP are expected to be a biomarker for assessment of exposure to DEP. In this study, a highly specific and sensit...