Liquid crystal monomers (LCMs) are critical components of laptop, television and smartphone screens. Given their ubiquity in the environment, these compounds are considered persistent pollutants, posing threats to marine life that scientists want to understand. Research published in ACS' Environmental Science & Technology provides initial evidence that LCMs from household electronics or electronic waste (e-waste) can accumulate in dolphin and porpoise tissues, including blubber, muscle, and brain, demonstrating their ability to cross the blood-brain barrier.
"Our research reveals that LCMs from everyday electronics are not just pollution — they're accumulating in the brains of endangered dolphins and porpoises," says Yuhe He, a researcher at City University of Hong Kong and a corresponding author of the study. "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."
LCMs control how light passes through handheld and large display screens, producing the sharp images consumers have grown to expect. Given these devices' widespread use, the chemicals have been found in indoor air, dust and even wastewater, eventually ending up in coastal environments. Previous studies also found that some LCMs pose health risks to humans and some aquatic species. However, less is known about how these pollutants move through marine food chains and whether they reach top predators. To determine this, Bo Liang, He and colleagues analyzed tissue samples from Indo-Pacific humpback dolphins and finless porpoises collected between 2007 and 2021 in the South China Sea, an important habitat for these endangered marine animals.
They screened the dolphin and porpoise blubber, muscle, liver, kidney and brain tissue samples for 62 individual LCMs. The analysis indicates that:
- Four compounds accounted for the majority of what was detected. Prior studies identified similar LCMs in the fish and invertebrates that these dolphins and porpoises eat, which the researchers say supports the idea that the pollutants enter through their diet rather than directly from water.
- Most of the LCMs found in dolphins and porpoises likely originated from television and computer screens, with smaller contributions from smartphones.
- Although the contaminants were most concentrated in blubber — a fatty tissue that often stores pollutants — the researchers were surprised to discover small amounts in other organs, particularly the brain, revealing potential health hazards such as neurotoxic risks.
- LCM levels in porpoise blubber have changed over time, generally increasing when liquid crystal display use was expanding and then declining in recent years as manufacturers have shifted to more LED displays.
In additional lab tests, several common LCMs, including the major four in these samples, altered gene activity such as those related to DNA repair and cell division in cultured dolphin cells. These results suggest that these compounds could negatively impact marine mammals. So, the researchers call for further investigation into the effects of LCM pollution on wildlife, highlighting the need for urgent regulatory action and improved e-waste disposal.
The authors acknowledge funding from the National Natural Science Foundation of China, Research Grants Council of Hong Kong, Ecology and Enhancement Fund, and Marine Conservation and Enhancement Fund, a Shantou University Scientific Research Initiation Grant, the National Science Foundation for Young Scientists of China, the Key Program of Marine Economy Development (Six Marine Industries) Special Foundation of the Department of Natural Resources of Guangdong Province, and the Innovation and Technology Commission of the Hong Kong SAR Government.
The paper's abstract will be available on Feb. 25 at 8 a.m. Eastern time here: http://pubs.acs.org/doi/abs/10.1021/acs.est.5c17767
