From pesticides to surfactants to personal care products, the list of contaminants in the environment constantly grows longer. For decades, researchers have been adding compounds or families of compounds to the list, outpaced by the development of new chemicals. “As soon as we identify a contaminant”—and it is scrutinized for adverse environmental or health effects, then regulated or phased out— “another comes to fill the space,” says Kevin V. Thomas, an environmental chemist at the University of Queensland in Australia.
Because this process can take a long time, by the time a compound of concern is on scientists’ radar, it has often already taken a toll. So Thomas led a pilot study to explore how archived high-resolution mass spectrometry (HRMS) data from environmental samples could speed up scientists’ understanding of emerging contaminants (Environ. Sci. Technol. 2018, DOI: 10.1021/acs.est.8b00365). By retrospectively analyzing the HRMS data, scientists could obtain a picture of where and when suspected contaminants occurred in the environment, even if researchers did not look for those particular compounds during earlier analyses.
In the past five years, advances in mass spectrometry such as increased sensitivity and affordability allowed many research groups to collect HRMS data of their samples, says Diana S. Aga, an environmental scientist from the University of Buffalo who was not involved in the study. Mass spectrometry analysis sorts chemical species based on their masses. In complex samples with thousands of chemicals, like those from wastewater, high-resolution instruments allow species to be distinguished by a fraction of a mass unit when they might have looked identical in low-resolution instruments. Using high resolution thus allows researchers to extract a detailed picture of what these environmental samples contain.
In the last few years, researchers have been storing the HRMS data for possible future use, says Thomas, since spectra contain so much information. As a result, there are now archives of HRMS data that can be mined in retrospective analyses to look for fingerprints that mark the presence of targeted compounds.
Eight research groups around the world decided to see what they could find by pooling data. They analyzed HRMS data previously collected from 48 wastewater, river, and groundwater samples from fourteen countries, including Mexico, Australia, and many European countries. Participants analyzed their data for the presence of a large number of targets, including those in current chemical contaminants databases such as the U.S. EPA’s CompTox Chemistry Dashboard and the European NORMAN Suspect List Exchange. Thomas performed quality control checks to ensure that all of the data were analyzed in comparable ways.
Surfactants were the most prevalent chemicals detected, including polyethylene glycol which was in 85% of the samples. The samples also contained numerous pharmaceuticals and their transformation products, including venlafaxine, an antidepressant, which was found in 68% of the samples. Most of these compounds are not subjects of targeted environmental screening or monitoring programs yet, says Thomas.
“This work demonstrates an important opportunity to develop a network and database” for where and when contaminants and their transformation products emerge in the environment, says Lisa B. Axe, an environmental scientist at the New Jersey Institute of Technology who was not involved in the study. In particular, retrospective analyses done over a long period of time could help researchers better understand how contaminants persist, change, or respond to remediation. The challenge, she says, is getting researchers to pool their data so that larger trends can be extracted.
Toward this goal, the researchers deposited their results online in the NORMAN Suspect List Exchange and EPA’s CompTox Chemistry Dashboard. Thomas hopes more researchers will contribute their archived HRMS data. He envisions an online platform where participating researchers could not only search for the occurrence of particular contaminants, but also match any new data to a constantly updating list of chemical suspects.