Author: Dr. Shelley Liu
Because people are exposed to many environmental exposures simultaneously (e.g. mixtures), it can be helpful to have summary scores of cumulative exposure. Summary scores have been shown to be useful in other fields (e.g. IQ scores in neurobehavioral research).
We conceptualized using “ exposome burden scores” to quantify cumulative exposure to mixtures, independent of a health endpoint. These summary scores can be used for biomonitoring, risk assessment and report-back to study participants. Our team has been developing the PFAS exposure burden calculator, an example of exposome burden scores applied to per- and polyfluoroalkyl substances (PFAS) mixtures.
What is the PFAS exposure burden calculator?
It’s a health informatics tool that quantifies a person’s total exposure to PFAS environmental toxins, and develops a common exposure burden scale across studies.
- Uses a person’s blood levels of measured PFAS analytes to estimate their “burden”, or cumulative exposure, to PFAS mixtures
- Provides a summary exposure score for exposure to PFAS mixtures and standard error (to account for imperfect estimation of total PFAS)
- Places PFAS burden scores onto a common scale based on nationally representative U.S. reference ranges, enabling comparisons of overall PFAS burden scores across people, studies and population sub-groups, even if they did not measure the same set of PFAS analytes
- PFAS burden scores are empirically more sensitive to detecting associations with health outcomes compared with using summed PFAS concentrations
- Provides robust and consistent findings even when studies do not measure the full set of PFAS analytes
- Empirically, PFAS burden scores are strongly correlated with extractable organofluorine (EOF) in the general population
- Item response theory-based data science methods are used to develop the calculator
- Offers a straightforward way to include exposure biomarkers with low detection frequencies, and reduces exposure measurement errors by considering both a participant’s PFAS concentrations and their exposure patterns to estimate their PFAS burden scores
What are some research questions and scenarios in which researchers could use PFAS burden scores?
- “Which population subgroups have higher cumulative exposure to PFAS mixtures?”
- “How can I report-back summary metrics about cumulative PFAS exposure to study participants?”
- “How do I include a summary measure of PFAS exposure as a predictor in disease risk calculators?”
- “Which physiological system is most perturbed by cumulative exposure to PFAS mixtures?”
- “How do I collapse lots of PFAS biomarker data into summary metric(s) for use as mediators and confounders?”
How can I use the PFAS Exposure Burden Calculator for my research?
You can access our free, point-and-click R/Shiny app here, for the 2017-2018 U.S. PFAS Exposure Burden Calculator. You can input the serum/plasma PFAS concentrations of your participants, and/or upload an Excel file, and our calculator will output a PFAS exposure burden score and standard error for each participant. It’s okay if you don’t have the concentrations of all the PFAS analytes – just leave those blank. We wrote a tutorial paper on using the PFAS Exposure Burden calculator.
What if I have any questions?
Feel free to email me at shelley.liu@mountsinai.org with any questions or if you’d like to collaborate – I’m always interested in new collaborations! I’d also love to hear your thoughts if you have any features you’d like to see me add, and if you’d like to contribute data to calibrating the PFAS Exposure Burden Calculator. We are currently extending the calculator to additional years and PFAS analytes.
Funding support:
The PFAS Exposure Burden Calculator is supported by a grant from the National Institute for Environmental Health Sciences (R01ES035804; PI: Liu).
Access the PFAS Exposure Burden Calculator:
https://pfasburden.shinyapps.io/app_pfas_burden/