Chemicals from LCD screens in the bodies of dolphins and porpoises

Chemicals used in the production of liquid crystal display (LCD) screens can accumulate in the bodies of marine mammals. A new study by Chinese researchers shows that so-called liquid crystal monomers (LCMs), used in the manufacture of televisions, computers and smartphones, end up in the aquatic environment and accumulate in the tissues of animals, which can pose serious health risks.

Electronics as a source of new pollution

Liquid crystal displays are among the most popular components of modern electronics. For their production, liquid crystal monomers are used, i.e. chemical compounds that impart appropriate optical properties to the displays. The scale of their application is enormous. It is estimated that by 2030 up to 74 million tons of LCD devices will enter the electro-waste stream annually.

The problem arises when disposing of these devices. Chemicals in the screens can enter the environment. LCMs are characterized by high persistence, bioaccumulation and potential toxicity. This means that they can persist in the environment for a long time and accumulate in organisms.

Dolphins and porpoises as indicators of ocean pollution

The study, the results of which were published in the journal Environmental Science & Technology, was conducted in the Pearl River estuary in the northern South China Sea, one of the world’s most industrialized areas. The region is also an important habitat for endangered cetacean species such as the Chinese humpback whale(Sousa chinensis) and the finless porpoise(Neophocaena phocaenoides).

Scientists analyzed tissue samples of 16 dolphins and 26 porpoises, obtained from dead individuals found in the region. Among other things, they examined muscle, brain, liver, kidney and subcutaneous fat. The results showed that liquid crystal monomers are commonly present in the tissues of these animals. Of the 62 LCM compounds analyzed, as many as 38 were detected in at least one sample. This is the first direct confirmation that substances used in the manufacture of electronic screens can accumulate in the bodies of wild marine mammals.

Pollutants build up in fat and brain

The concentrations of total liquid crystalline monomers in the tissues studied ranged from below the limit of quantification to 203 ng/g dry weight. The average concentration was 53.6 ± 65.3 ng/g in dolphin tissues and 32.7 ± 41.8 ng/g in porpoises.

The highest amounts of these compounds were detected in fat-rich tissues. In dolphins, the highest levels were found in subcutaneous fat and muscle, where average concentrations were 57.9 ± 70.8 ng/g and 66.6 ± 68.5 ng/g, respectively. In porpoises, the highest concentrations were found in subcutaneous fat (45.7 ± 53.5 ng/g), as well as brain (38.7 ± 36.8 ng/g).

Of particular concern is the presence of LCM in brain tissue. Few environmental contaminants are able to penetrate the blood-brain barrier, so the discovery raises concerns about the potential for side effects in the nervous systems of these animals.

Several compounds are responsible for most LCM contamination

Analysis of the chemical composition showed that four compounds are responsible for more than 80 percent of all liquid crystal monomers detected. These are MPCB, PPB, PeCHPrB and MOPrCHB – substances commonly used in TV, computer and smartphone screens.

The dolphins’ adipose tissue was dominated by the compound PPB, which accounted for about 45 percent of all LCMs detected. In contrast, MOPrCHB was most prevalent in the brains of dolphins , accounting for 75 percent of these compounds. In porpoises, PPB and PeCHPrB were most frequently detected.

The researchers also observed a strong correlation between LCM concentrations in fat and muscle. The correlation coefficient was 0.77 for fat and 0.96 for muscle, suggesting similar exposure pathways in both species, most likely related to diet.

Televisions and computers the main source of LCM

To determine the sources of contamination, the researchers conducted a statistical analysis of the chemical profiles of LCMs. The results indicate a very strong similarity between the composition of compounds in cetacean tissues and the chemical profile of electronic screens. The correlation coefficient was 0.96, indicating a clear link between compound emissions from electronic devices and marine pollution.

LCD televisions account for the largest share of these emissions, accounting for about 56.8 percent of detected LCMs. This is followed by computer monitors with a share of 23.7 percent, smartphones with 11 percent, and other computer screens (8.5 percent).

Technological changes affect pollution levels

The researchers also analyzed changes in LCM concentrations in porpoise tissues between 2007 and 2021. They found that average values were significantly higher in the 2007-2017 period than in the 2018-2021 period. The time trend shows an increase in LCM levels between 2007 and 2015, a stabilization between 2015 and 2017, and then a decrease after 2017. Researchers link these changes to the increasing share of LED technology, which is gradually replacing traditional LCD displays.

Cellular studies point to potential health effects

To evaluate the potential biological effects of LCM accumulation, experiments were conducted on cetacean skin and kidney cells. Eight compounds most commonly found in the tissues studied were tested.

Two of them – MOPrCHB and EDFPPB – reduced cell survival at higher concentrations. This effect appeared at levels of 258 ng/ml for MOPrCHB and 51 ng/ml for EDFPPB.

Analysis of gene activity showed that LCMs can affect many biological processes, including tissue development, cardiovascular function, inflammatory responses, and cell cycle and DNA replication. Specifically, MOPrCHB inhibited the activity of genes responsible for cell division and copying genetic material, which was consistent with the observed decrease in cell viability in the experiment.

The problem is growing with the amount of electro-waste

Although LCM concentrations in cetacean tissues are currently lower than the levels of classical pollutants such as DDT or PCBs, the study’s authors emphasize that their importance may increase with increasing amounts of electro-waste.

Liquid crystal monomers may also interact with other environmental pollutants such as PFAS compounds, heavy metals and microplastics. This combination of factors is likely to increase the pressure on marine organisms. According to the authors, further research is needed on the toxicity of LCMs, as well as measures to reduce emissions of these pollutants associated with the growing mountain of electro-waste.

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Source:

Liquid Crystal Monomers Released from LCD Displays Accumulate in Endangered Marine Cetaceans Triggering Health Concerns,Danyang Tao, Chengzhang Li, Yajing Sun, Yuefei Ruan, Qianqian Jin, Jiaji Sun, Yichun Lu, Brian C. W. Kot, Paul K. S. Lam, Fengchang Wu, Jia He, John P. Giesy, Kurunthachalam Kannan, Bo Liang, Wenhua Liu, Lin Zhang, Yunsong Mu, Kenneth M. Y. Leung, and Yuhe He, Environmental Science & Technology Article ASAP, DOI: 10.1021/acs.est.5c17767