Screen Chemicals Are Accumulating in Dolphin and Porpoise Brains, New Study Finds

The chemicals that make your phone screen sharp are turning up inside the brains of endangered dolphins.

A study published in ACS Environmental Science and Technology has found liquid crystal monomers - chemical compounds essential to the display technology in laptops, televisions, and smartphones - accumulating in the tissue of Indo-Pacific humpback dolphins and finless porpoises collected from the South China Sea between 2007 and 2021. The detection of these compounds in brain tissue is particularly significant: it indicates that the chemicals can cross the blood-brain barrier, a selective membrane that normally limits what enters the central nervous system.

What Liquid Crystal Monomers Are and Where They Come From

Liquid crystal displays work by using liquid crystal compounds to control how light passes through pixels. The liquid crystal monomers (LCMs) are the building blocks of this system - small organic molecules that align in response to electric fields, allowing the screen to switch between light and dark states pixel by pixel. Modern displays use hundreds of different LCM formulations, and the compounds are present in virtually every screen-based device sold globally.

LCMs enter the environment through multiple pathways. They are present in indoor air, household dust, and wastewater from device manufacturing and disposal. As electronics are discarded and improperly processed through e-waste streams, LCMs are released into the environment - including coastal waters that serve as habitat for dolphins and porpoises. Previous research had found some LCMs in indoor environments and in some aquatic species, but evidence of accumulation in large marine mammals, and specifically in brain tissue, was limited.

What the Dolphin and Porpoise Samples Revealed

The research team, led by Yuhe He at City University of Hong Kong, analyzed tissue samples from Indo-Pacific humpback dolphins and finless porpoises - both species listed as endangered or vulnerable - collected from the South China Sea. The samples included blubber, muscle, liver, kidney, and brain tissue, and were screened for 62 individual LCM compounds.

Four compounds accounted for the majority of what was detected across all tissue types. Prior studies had identified similar LCMs in the fish and invertebrates these animals eat, which the researchers interpret as evidence that the primary exposure route is dietary - the chemicals enter through food rather than directly from water contact. The analysis indicated that most detected LCMs likely originated from television and computer screens, with smaller proportional contributions from smartphone displays.

As expected from their chemical properties, LCMs were most concentrated in blubber - the fatty tissue that forms the outer layer of cetaceans and acts as a depot for lipophilic (fat-soluble) compounds. But their detection in brain tissue is what distinguishes this finding from previous e-waste chemical studies. The blood-brain barrier in marine mammals is generally considered an effective filter against many contaminants; the presence of LCMs in brain tissue suggests some compounds in this class are sufficiently lipophilic or have the right structural characteristics to pass through it.

Health Implications Still Uncertain

The study establishes the presence of LCMs in dolphin and porpoise tissues, including the brain, but does not assess the health consequences of that accumulation. The toxicological profile of most LCMs in marine mammals is poorly characterized. Some compounds in the class have been shown to cause adverse effects in fish and in laboratory mammal models at sufficient concentrations, but whether the tissue concentrations observed in this study are high enough to produce physiological effects is not yet known.

"Our research reveals that LCMs from everyday electronics are not just pollution - they're accumulating in the brains of endangered dolphins and porpoises," said He. "This is a wake-up call: the chemicals powering our devices are now infiltrating marine life, and we must act now on e-waste to protect ocean health and, ultimately, ourselves."

The temporal scope of the sample collection - spanning 2007 to 2021 - offers a window into whether accumulation is changing over time as global electronics consumption has grown. The study does not report trends over that period, which would be valuable context for assessing whether the problem is worsening.

The Broader E-Waste Problem

Global e-waste generation exceeded 62 million metric tons in 2022 according to UN estimates, with only about 22% formally recycled. The remainder enters waste streams in ways that often involve open burning, acid leaching, or landfill disposal - all of which release chemical constituents including LCMs into air, soil, and water. Coastal regions in Southeast Asia, which include the South China Sea habitat of the species studied here, are major processing sites for informally recycled e-waste from higher-income countries.

The connection between informal e-waste processing in coastal regions and chemical accumulation in the marine mammals that inhabit those waters is plausible and consistent with the study's findings, though the precise exposure pathways and relative contributions of different e-waste sources remain to be quantified.

This study adds liquid crystal monomers to a growing list of chemicals of concern for marine mammals - a list that already includes polychlorinated biphenyls, per- and polyfluoroalkyl substances (PFAS), flame retardants, and pharmaceuticals. The novelty here is the source: the screens we use every day.