In our daily lives, countless chemicals are quietly affecting our environment and health. Polychlorinated Naphthalenes (PCNs), as highly toxic persistent organic pollutants, are one of them. They were widely used in electrical equipment and industrial lubricants. Studies have shown that PCNs can be passed through the food chain, affecting aquatic organisms, terrestrial animals, and eventually even human health. PCNs were included in the Stockholm Convention in 2015 and have been banned from intentional production. Currently the main source is unintentional emissions from industry. Understanding the emission trend of PCNs is not only crucial for environmental monitoring, but also helps to form effective policies and regulations to protect public health.
The Motivation Behind Our Study
Although current production of PCNs has ceased, their high bioaccumulation and persistence means that they may persist in our environment for many years. At the beginning of our study, we found a lack of data on long-term emission trends of PCNs. Methods for estimating emissions over production periods were not clear. Could we better quantify historical PCN emissions using modern statistical analysis techniques?
Thanks to previous studies by the group, we have data on several sources of unintentional emissions. However, current inventories of unintentional emissions are only available for individual regions or time periods, and consider a small variety of sources. A systematic inventory of unintentional emissions with a global perspective is still lacking. From a global perspective: How many PCNs are emitted annually? Which emission sources are most concerning? What are the primary emission areas?
Based on the above study, we further discuss the future trend of PCNs emissions. We want to know: what will happen to the future emissions of PCNs if they are not controlled?
The core objective of the study is to quantify global emissions of PCNs from 1912 to 2050 to reveal their potential impacts on ecosystems.
Research Challenges
Data collection was one of the major challenges we encountered during the research process. Historical data are difficult to obtain for many countries. In addition, published data are discrete and inconsistent. To ensure the accuracy of our results, we prioritized officially reported data. For activity level data, we prioritized the use of the same official data to reduce errors caused by different database estimation methods. Technical tools such as the BETR-Global transmission model, sensitivity analysis, and Monte Carlo analysis were used to assess uncertainty.
Key findings
Through our analysis, we found that global emissions of PCNs experienced significant changes from 1912 to 2050. The results show that 468,014 t of PCNs were emitted from historical production, with the majority of cumulative PCN emissions entering the atmosphere. Total unintentional emissions from 2000–2020 are 11,534 t. Global emissions of PCNs are 293.5 t (15.8 kg TEQ) in 2020, with municipal waste incineration as the major source and West Central Asia being the major emission region. Future PCN emissions may experience fluctuations, with projected changes ranging from a decrease of 29% to an increase of 347%.
In conclusion, as an organic pollutant with potential ecological risks, PCNs have played an important but complex role in the industrialization history of human beings. By studying the global emissions of PCNs from 1912 to 2050, we not only revealed their historical changes and future trends, but also provided valuable data support for the formulation of related policies.