The Unep study, which the Global Environment Facility funded, was conducted in 42 countries in regions where data on persistent organic pollutants is limited.(Photo by Doaa Adel/NurPhoto via Getty Images)
Levels of some chemical pollutants, including the insecticide DDT, are lower in humans and in the environment but new ones “keep popping up”, research by the United Nations Environment Programme (Unep) has found.
Data from its global study of persistent organic pollutants (POPs) found that there has been a global decline in the 12 initially listed in the 2004 Stockholm Convention on Persistent Organic Pollutants.
This is a global treaty to protect human health and the environment from chemicals that remain intact in the environment for long periods, become widely distributed geographically, accumulate in the fatty tissue of humans and wildlife and can have harmful effects on human health and on the environment.
The report attributes the declining trend to regulatory actions that have been taken since the global treaty came into force. But their replacements, often later banned because of similar properties, such as per-and polyfluoroalkyl substances (PFAS), were detected at high levels.
These hazardous chemicals are linked to cancer, liver damage, decreased fertility, as well as the increased risk of asthma and thyroid disease because of their endocrine-disrupting properties.
The Unep study, which the Global Environment Facility funded, was conducted in 42 countries in regions where data on persistent organic pollutants is limited, including Africa, Asia, Latin America and the Caribbean and the Pacific Islands to monitor the 30 listed under the Stockholm Convention. Samples were collected between 2016 and 2019.
In Africa, the research was done in the Democratic Republic of the Congo, Egypt, Ethiopia, Ghana, Kenya, Mali, Morocco, Mauritius, Nigeria, Senegal, Tanzania, Togo, Tunisia, Uganda and Zambia.
“Chemicals are continually being created and introduced into the environment,” the study noted. “Among these, POPs, including those termed ‘forever chemicals’, pose enduring risks due to their long-lasting presence in the environment and their impacts on human health and ecosystems.”
Persistent organic pollutants “remain omnipresent”, despite efforts to reduce their use and production, said Andrea Hinwood, Unep’s chief scientist. “Monitoring the concentrations of POPs in the environment and in our own bodies is vital, especially in low and middle-income countries, to support their assessment of contamination, emissions and exposure to POPs for informed decision-making.”
Developing countries and countries with economies in transition encounter “profound” difficulties in managing contamination, emissions and exposure to persistent organic pollutants.
“This situation is amplified by an expanding list of POPs chemicals and inadequate capacities for monitoring, regulating and managing of POP contaminants and waste. Enhanced support and strategic interventions are critical to overcome these barriers and protect both the environment and public health.”
The list of 30 persistent organic pollutants included pesticides and industrial chemicals, as well as unintentionally released POPs, which are by-products of industrial processes and from incomplete combustion, for example, through the open burning of waste.
They were found in every one of more than 900 collected samples in air, water, human milk, soil, beef, milk, milk powder, butter, mutton, pork, chicken, eggs, fish, shellfish, oil and other items.
Other persistent organic pollutants “are present everywhere”, including in areas far from any known source of contamination. Long-regulated chemicals, such as dieldrin and polychlorinated biphenyls (PCBs) were detected at elevated levels in the air across the African continent, the Caribbean and Latin America.
DDT, once used in agriculture and now highly restricted, has decreased by more than 70% in human milk samples since 2004 on a global average, the study found. Still, DDT remains the most prevalent persistent organic pollutant in human milk, particularly in countries where the chemical is intensively used.
There has been a measurable decrease in the global levels of other legacy persistent organic pollutants such as PCBs and dioxin-like POPs (dl-POPs).
“This indicates the impact of restricting or banning the production and usage of legacy POPs and improving waste and emission management has been successful. However, concentrations of POPs in some areas remain high. Globally, DDT accounted for the largest proportion of POPs on average, followed by chlorinated paraffins and PCBs.”
Industrial persistent organic pollutants such as chlorinated paraffins and polychlorinated biphenyls accounted for about 60% of POPs in human milk in the Asia-Pacific region and 40% in the African, Latin America and Caribbean regions.
“The high levels of new POPs listed under the Stockholm Convention such as short-chain chlorinated paraffins raise concerns over their sources of exposure, indicating the need to reduce exposure and the benefit of monitoring to understand the nature of potential and exposures and the benefits of actions to reduce exposures,” the study said.
Some banned chemicals have been replaced with other chemicals, which were later found to also have persistent organic pollutant properties such as PFAS. Of the thousands of PFAS, three key chemicals (PFOS, PFOA, PFHxS) are listed under the Stockholm Convention. All were found in human milk. PFAS were also found in drinking water in remote islands, at levels far exceeding European Union and United States standards.
More than 290 air samples were analysed for organochlorine pesticides, industrial chlorinated persistent organic pollutants, and brominated flame retardants and almost 200 samples were analysed for dl-POPs. “In general, declines were observed throughout the POPs and countries. Despite a strong decline (more than 60%) determined for DDT, it remained with the highest values by scale.”
The highest DDT values were found in the Democratic Republic of the Congo and Solomon Islands.
For organochlorine pesticides, including indicator PCBs, relatively high levels were found in Zambia and Tanzania. The highest value for PFAS was found in Zambia. Brominated flame retardants were found at higher levels in the samples collected from the African region than those from the other regions.
Hexabromocyclododecane and polybrominated diphenyl 209 were found at relatively high levels in samples from Zambia and Mongolia. Samples collected in Egypt and Zambia were found with relatively high levels of dl-POPs than the other samples.
According to Unep, newly-listed persistent organic pollutants are increasingly difficult to monitor, even by the world’s top laboratories.
Data collection is improving but with more labs in low-income countries participating, including in the Unep global interlaboratory assessments, the quality of persistent organic pollutant analysis should continue to improve.
“Governments need not be pulled into a toxic game of hide-and-seek, where one regulated POP is replaced with a new one,” said Jacqueline Alvarez, chief of the chemicals and health branch of Unep.
“This troubling pattern means these substances are still present in products we use, eat, wear, as well as in our air and water. This highlights the risk of regrettable substitutions of banned POPs and the need to prioritise sustainability in industrial product design and consumer behaviour.”
The findings are published as governments gather this week in Geneva for an ad hoc working group on the establishment of a science-policy panel on chemicals, waste and pollution prevention.