About

Krystal Pollitt, PhD, P.Eng., is an Associate Professor of Epidemiology (Environmental Health) at Yale School of Public Health and an affiliated faculty member at the Yale Institute for Global Health. Her research applies exposomic approaches to investigate the influence of environmental factors on disease. She emphasizes the need for robust, reliable, reproducible, and rigorous analytical and computational techniques to operationalize the exposome framework for application in population studies. Her work has focused on addressing technical hurdles related to the systematic and comprehensive measurement of environmental chemicals using high-resolution mass spectrometry. Her research team has pioneered technology in this area, contributing significantly to the field of environmental health sciences.

Research topics

• Computer Science
• Artificial Intelligence
• Environmental chemistry
• Chemistry
• Medicine
• Biology
• Environmental health
• Operating system
• Virology
• Database
• Chromatography
• Environmental science
• Genetics
• Pathology
• Biochemistry

Selected publications

• Approaching a 0% False Positive Rate for PFAS Determination Leveraging Only MS1 Data

  Environmental Science & Technology · 2026-01-30

  articleCorresponding

  Liquid chromatography high-resolution tandem mass spectrometry (LC-HRMS/MS) is commonly used for the analysis of per- and polyfluoroalkyl substances (PFAS). Targeted approaches with LC-HRMS/MS often cover less than 30% of PFAS across various matrices and hence nontargeted strategies are necessary to enhance identification coverage. We expanded FluoroMatch Suite, a nontargeted PFAS data-processing software, to leverage full-scan (MS1) data for highly accurate formula prediction and Kaufmann analysis. Software features include Kaufmann analysis with isoline cutoffs determined using kernel density based on an EPA PFAS data set and an 11-step formula prediction algorithm. Application of the FluoroMatch Suite with the MS1 extension to AFFF contaminated soil revealed 179 PFAS-confirmed features. Kauffman 95% isoline cutoffs captured 94% of the confirmed PFAS and removed 96% of features assigned as likely non-PFAS. The PFAS-formula prediction introduced in this manuscript had a false positive rate of 26% and a false negative rate (no predicted formula) of 30%. Using a novel homologous series voting algorithm, where the predominant subclass from formula prediction were used to predict all formulas for the homologous series, we achieved a 0% false positive rate and 6% false negative rate in formula prediction. The novel nontargeted algorithms developed in this study proved to be highly accurate and by leveraging MS1 data enhances the capacity to identify unknown PFAS in complex environmental matrices.

  PublisherDOI

• Association of per- and polyfluoroalkyl substances (PFAS) exposure with cognitive function in firefighters

  Journal of Exposure Science & Environmental Epidemiology · 2026-03-25

  articleOpen access

  BACKGROUND: Evidence on cognitive function in relation to per- and polyfluoroalkyl substances (PFAS) exposure in firefighters is scarce. OBJECTIVE: We conducted a pilot study aiming to explore the associations of individual PFAS analyte and PFAS mixture with domain-specific cognitive performance in firefighters. METHODS: Firefighters (n = 65), who were actively serving four cities in Central Texas 2003-2025, were assessed for global cognition and processing speed measured by the NIH Toolbox Cognition Battery. Whole blood samples were collected from these participants and analyzed by liquid chromatography-tandem mass spectrometry for 24 PFAS analytes. Linear regression models were used to evaluate associations between cognitive performance and both individual PFAS analytes and the overall 24-PFAS mixture. Additionally, quantile g-computation and Bayesian Kernel Machine Regression (BKMR) were applied to investigate associations between 6-PFAS mixture and cognitive performance, with adjustment for potential covariates. RESULTS: Six PFAS analytes including potassium perfluoro-1-octanesulfonate (PFOS), perfluoro-n-octanoic acid (PFOA), perfluoro-n-heptanoic acid (PFHpA), perfluoro-n-nonanoic acid (PFNA), perfluoro-n-decanoic acid (PFDA), and potassium perfluoro-1-hexanesulfonate (PFHxS) were detected in the least 70% of participants. PFOS was negatively associated with scores of processing speed (ß = -0.58 p < 0.001). Neither the 6-PFAS mixture nor the 24-PFAS mixture was associated with either cognitive domain. SIGNIFICANCE: These preliminary findings may inform future research seeking to clarify the biological pathways linking PFAS exposure to cognitive outcomes and to explore possible modifiable factors related to cognitive health in firefighters. They might also underscore the potential value of continued effort to minimize workplace PFAS exposure for this occupational group. IMPACT: Our study provides the first data on PFAS exposure and cognitive performance for firefighters. Our analysis revealed that PFOS was the primary contributor among the PFAS mixture (consisting of PFOS, PFOA, PFHxS, PFHpA, PFNA, and PFDA) linked to reduced processing speed scores in firefighters. Our findings pave the way for future, larger studies that observe firefighters for longer duration to develop confident estimates of cognitive health in relation to PFAS exposure. These data could inform analyses in support of workplace exposure reduction efforts and revision of preventive health care for first responders.

  PublisherOA PDFDOI

• Targeted and non-targeted analyses of per-and polyfluoroalkyl substances in newborn dried blood spots and risk of childhood acute lymphoblastic leukemia

  Journal of Exposure Science & Environmental Epidemiology · 2026-04-14

  articleOpen access

  Abstract Background Per- and polyfluoroalkyl substances (PFAS) have carcinogenic potential but are understudied in relation to childhood cancers. Objective We examined associations between targeted and non-targeted PFAS measured in newborn dried blood spots (DBS) and the risk of childhood acute lymphoblastic leukemia (ALL) in Los Angeles County, California, accounting for maternal and child characteristics. Methods ALL cases ( n = 125) diagnosed before age 18 years during 2000–2015 and controls ( n = 219) were selected from a registry-based study using stratified sampling based on birth year and birth address within a PFAS-contaminated water district according to the USEPA Third Unregulated Contaminant Monitoring Rule. We calculated design-based odds ratios (OR) and 95% confidence intervals (CI) for the effect of PFAS exposures, independently and adjusting for other PFAS. We also conducted non-linear and stratified analyses. Results Of the 17 PFAS quantified using targeted analysis, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) had the highest mean concentrations in DBS, with 4690 and 10,307 pg/g dried blood among cases compared to 4245 and 8142 pg/g dried blood among controls, respectively. The highest risks were observed for the 4th exposure quartile compared with the 1st quartile (PFOA OR = 1.56, CI: 0.42, 5.73; PFOS OR = 1.64, CI: 0.44, 6.14). In non-linear statistical analyses of joint PFOA and PFOS exposures adjusted for other detected PFAS, we also found that ALL risk increased with increasing levels of log2-PFOA and log2-PFOS. Non-targeted analysis identified 26 additional PFAS, for which elevated risk of childhood ALL was associated with a doubling of C 4 HF 7 O 3 exposure (OR = 5.04, CI: 1.08, 23.63) and the highest quartile of C 10 HF 19 O 5 exposure (OR = 5.20, CI: 1.15, 23.56). Associations were generally stronger among non-Hispanic participants compared to Hispanic participants, but these analyses were limited by small sample sizes and should be considered exploratory. Significance There was some suggestion that high PFOA and PFOS exposures measured at birth, as well as certain PFAS detected by non-targeted approaches, were related to childhood ALL risk. Impact statement This study of childhood ALL in Los Angeles County, California found increased risk among children with the highest PFOA and PFOS levels measured in neonatal dried blood spots. These risks were stronger among non-Hispanic children, and the greatest risk was observed for joint PFOA and PFOS exposure adjusting for other detected PFAS and maternal/child characteristics. We also observed possible associations with PFAS discovered by non-targeted analysis. Our results highlight the utility of dried blood spots as a matrix for assessing early life exposures as well as the value of hybrid targeted and non-targeted approaches to measure PFAS in health studies.

  PublisherDOI

• Evaluating 1,4-Dioxane Exposure in Long Island, New York: Integrating Environmental, Biological, and Metabolomic Measures

  Environmental Science & Technology · 2026-03-13

  articleOpen accessSenior author

  1,4-Dioxane (1,4-DX), found in solvents and personal care products, is a potential carcinogen with limited exposure data. Tap water, blood samples, and interviews were collected from 92 residents of Long Island, New York, an area with historically high 1,4-DX drinking water concentrations. We assessed the relationship between water and blood 1,4-DX concentrations, evaluated exposure determinants, and compared metabolomic profiles by exposure status. 1,4-DX was detected in 32% of water and 24% of blood samples; 24% of water samples exceeded New York’s Maximum Contaminant Level (MCL) of 1 μg/L. Water and blood 1,4-DX concentrations were not correlated (r = −0.11, p = 0.32). Older homes (built <1960) and those without a whole-house treatment system were more likely to have detectable 1,4-DX in tap water (p < 0.05). Water consumption and personal care product use were not associated with blood 1,4-DX. Metabolomic analyses revealed small but significant differences in redox and energy metabolism among those with and without detectable water 1,4-DX (fold change <20%, false-discovery-rate-corrected p < 0.05). The lack of correlation between 1,4-DX in paired water and blood samples suggests other exposure sources or differing time windows captured by sample types. Larger studies could clarify exposure determinants and metabolomic impacts to better assess the potential health burden of 1,4-DX.

  PublisherDOI

• Measuring the exposome: a practical guide for using wearable passive samplers to assess environmental influences

  Exposome · 2026-01-01

  articleSenior author

  Abstract Wearable passive samplers present tremendous opportunity for measuring the exposome. These tools offer a user-friendly and cost-effective approach to assess personal exposure, enabling access to remote communities and under-researched vulnerable populations. Use of these wearable devices has gained popularity over the past two decades but before these tools can be adopted for routine use in large-scale health studies, they require standardization to ensure data reproducibility. With the objective of harmonizing wearable passive sampler use, this paper serves as a guide to available technologies (Fresh Air samplers, commercial silicone wristbands, custom silicone bands, and the silicone brooch) and best practices for assessing exposure to environmental chemicals. We discuss the optimal duration to wear these sampling tools, essential quality control and quality assurance measures, chemical analysis approaches, and strategies to interpret measured exposures. We also propose minimum guidelines for sample collection and reporting data to foster measurement standardization and secondary analysis. Strategies to improve data transparency through harmonization will enable comparability of the comprehensive measures of the exposome using wearable passive samplers.

  PublisherDOI

• Quantifying PFAS-Omics Burden Scores for Nontargeted Analysis Using Multidimensional Item Response Theory: An Exploratory Analysis of Novel and Legacy PFAS in Cord Blood

  Environmental Science & Technology · 2026-02-18

  articleOpen access

  Fetal development is a vulnerable period for exposure to per- and polyfluoroalkyl substances (PFAS). However, certified analytical standards do not exist for many PFAS, limiting our ability to quantify overall exposure burden to PFAS as a chemical class. PFAS-focused nontargeted analysis (NTA) enables detection of PFAS for which chemical standards may not exist. The overall objectives of this study were to provide a more comprehensive picture of PFAS exposure in cord blood, develop cumulative exposure burden scores for the PFAS detected, and evaluate differences in the infant's PFAS burden score with respect to mother's parity. We measured PFAS using targeted and NTA methods in cord blood samples collected between 2003 and 2006 in the HOME Study (Cincinnati, Ohio). Using NTA, we putatively identified 42 PFAS in cord blood, 4 of which were also detected in targeted analysis. We summarized an infant's overall prenatal exposure burden to PFAS using item response theory methods. We constructed two scores, one based on PFAS concentrations from targeted analysis ("PFAS exposure burden scores"), and one based on relative abundance from NTA ("PFAS-omics scores"). As expected, infants with multiparous mothers had significantly lower PFAS exposure burden scores than those with nulliparous mothers, but these disparities were not present when comparing their PFAS-omics scores. Our results show that infants are exposed to a wide range of PFAS, including perfluorinated chemicals, polyfluorinated chemicals, and fluorotelomers, before birth. Further, PFAS-focused NTA can help estimate total exposure to PFAS. Lastly, reported disparities in PFAS exposure burden across parity may depend on the panel of assessed PFAS and their half-lives.

  PublisherOA PDFDOI

• Filling the Gaps in PFAS Detection: Integrating GC-MS Non-Targeted Analysis for Comprehensive Environmental Monitoring and Exposure Assessment

  Environmental Science & Technology Letters · 2025-01-23 · 26 citations

  articleOpen access

  Per- and polyfluoroalkyl substances (PFAS) have garnered increasing attention in recent years and non-targeted analysis (NTA) has become essential for elucidating novel PFAS structures. NTA and PFAS research have been dominated by liquid chromatography - mass spectrometry (LC-MS) with gas chromatography - mass spectrometry (GC-MS) used less often as evidenced by bibliometrics. However, the performance of GC-MS in NTA studies (GC-NTA) rivals that of LC-ESI-MS and GC-MS is shown to cover a complimentary chemical space. An LC-ESI-MS amenability model applied to a list of approximately 12,000 PFAS revealed that less than 10% of known PFAS chemistry is predicted to be amenable to typical LC-MS analysis. Therefore, there is strong potential for applying GC-MS methods to more fully assess the PFAS environmental contamination landscape, uniquely shedding light on both known and novel PFAS, especially within the chemical space realm of volatile and semi-volatile PFAS. Waste streams from fluorochemical manufacturing facilities have been heavily studied using LC-MS and targeted GC-MS; however, GC-NTA is needed to discover novel PFAS that are not amenable to LC-MS emitted from facilities. Studies on the incineration of PFAS-containing materials, such as aqueous film forming foam, have focused on the destruction of parent compounds and little is known about the transformation products formed during such processes. GC-NTA holds the potential to elucidate transformation products formed when PFAS are incinerated. Wastewater treatment plants and landfills are known sources of PFAS to the environment, yet GC-NTA is needed to understand air emissions of PFAS and PFAS transformation products from these sources. Consumer products are known to lead to indoor exposures to PFAS via emissions to air and dust but research in this area has either used LC-MS or targeted GC-MS. Despite the challenges with advancing GC-NTA, we call on NTA researchers, grantors, managers, and other stakeholders to recognize the potential and necessity of GC-NTA in PFAS research so that we may face these challenges together.

  PublisherOA PDFDOI

• Shedding Light on PFAS Dark Matter Using a Novel GC-HRMS Approach

  Environmental Science & Technology · 2025-11-17 · 1 citations

  articleOpen accessSenior authorCorresponding

  With thousands of documented perfluoroalkyl and polyfluoroalkyl substances (PFASs), novel methods are needed to comprehensively characterize these fluorinated compounds in the environment, biota, and humans. Despite being the most common approach, liquid chromatography high-resolution mass spectrometry (LC-HRMS) only covers a fraction of PFASs. To address this gap, we developed a nontargeted gas chromatography high-resolution mass spectrometry (GC-HRMS) workflow to extend coverage of the PFAS chemical space, developing and incorporating the most extensive GC HRMS PFAS libraries to date covering over 1,900 electron ionization (EI) and positive chemical ionization (PCI) predicted and experimental spectra. Five environmental and biological matrices were assessed: aqueous film forming foam (AFFF), industrial outfall, municipal leachate, residential floor dust, and human blood. A novel compound was identified (2-(perfluorohexyl)ethanethiol) in multiple AFFF formulations. A rarely monitored PFAS was additionally detected (N-methyl-N-(2-hydroxyethyl)perfluorooctanesulfonamide, N-MeFOSE) in human blood, industrial outfall, municipal leachate, and residential floor dust at high frequency and abundance. A comparison to LC-HRMS approaches for leachate and blood showed no overlap between annotated PFASs. The nontargeted workflow presented here provides essential tools to expand PFAS monitoring capabilities and identify previously undetected compounds that may pose significant health and environmental risks.

  PublisherOA PDFDOI

• Emerging PFAS in songbird eggs from a Belgian hotspot site

  Environmental Research · 2025-10-17 · 1 citations

  article
  PublisherDOI

• Exposure to per‐ and polyfluoroalkyl substances in residential settled dust and risk of childhood acute lymphoblastic leukemia

  International Journal of Cancer · 2025-02-14 · 13 citations

  articleOpen access

  Abstract Per‐ and polyfluoroalkyl substances (PFAS) are ubiquitous. Young children are commonly exposed to these chemicals via ingestion of settled dust. Several PFAS have been associated with cancers in adults, yet little is known about the risk in children. We investigated whether PFAS concentrations in residential dust were associated with childhood acute lymphoblastic leukemia (ALL). Vacuum bags were collected in homes of 178 children diagnosed with ALL and 204 healthy controls (age 0–7 years) residing in California (2001–2007). Dust samples were sieved and analyzed for 19 PFAS using targeted liquid chromatography mass spectrometry analysis. The effects of individual PFAS and PFAS mixtures were estimated for eight PFAS with at least 50% above the limit of quantification (LOQ) using logistic regression, G‐computation, and generalized additive modeling (GAM). In the model mutually adjusting for eight PFAS, a statistically significant association was seen only for N ‐ethyl perfluorooctane sulfonamido acetic acid (EtFOSAA) (OR continuous = 1.40, 95% CI = 1.05–1.86 and , 95% CI = 1.16–5.71). Using G‐computation, the eight PFAS mixture was positively associated with childhood ALL (OR = 1.60, 95% CI = 1.15–2.24), with positive weights for EtFOSAA, perfluoro‐ n ‐hexanoic acid (PFHxA), perfluoro‐1‐decanesulfonate (PFDS), and perfluoro‐1‐octanesulfonate (PFOS), and negative weights for perfluoro‐1‐hexanesulfonate (PFHxS) and bis(1H,1H,2H,2H‐perfluorooctyl)phosphate (6:2 diPAP). Using GAM, the OR for the mixture reached a maximum of 2.24, at the highest value of log10 EtFOSAA and lowest value of log10 PFHxS. Exposure to a mixture of PFAS in settled dust was associated with an overall elevated risk of childhood ALL, with EtFOSAA and PFHxS being the main contributors to the positive and negative weights, respectively.

  PublisherOA PDFDOI

Frequent coauthors

• Frank J. Kelly

  Imperial College London

  63 shared

• Ian Mudway

  MRC Centre for Environment and Health

  63 shared

• Roy M. Harrison

  University of Birmingham

  62 shared

• Maciej Strak

  National Institute for Public Health and the Environment

  60 shared

• Bert Brunekreef

  52 shared

• Flemming R. Cassee

  National Institute for Public Health and the Environment

  42 shared

• Nicole Janssen

  41 shared

• Maaike Steenhof

  41 shared

Education

• Ph.D., Environmental Health

  Yale University

  2008

• M.S., Environmental Health

  University of California, Berkeley

  2003

• B.S., Environmental Science

  University of California, Berkeley

  2001