How Banned Pesticides Still Travel Through Our Skies
Despite being banned for decades, organochlorine pesticides continue to circulate through our atmosphere, embarking on invisible journeys that span continents and generations.
Imagine a pesticide applied to a field in the 1960s, now settling on a remote mountaintop or polar ice cap. This is the legacy of organochlorine pesticides (OCPs), a group of chemicals including DDT that were banned in most Western nations decades ago yet continue to travel through our atmospheric highways. These persistent organic pollutants (POPs) resist degradation, evaporating into the air and journeying thousands of miles before depositing in ecosystems far from their original application sites 3 . Sixty years after Rachel Carson's "Silent Spring" first alerted the world to their dangers, scientists continue to track these invisible travelers through sophisticated air monitoring networks, revealing how chemicals of the past remain very much present in our environment today 2 .
Visualization of atmospheric transport of persistent pollutants across the globe
Organochlorine pesticides include notorious chemicals like DDT, chlordane, and hexachlorocyclohexane (HCH). Their molecular structure makes them exceptionally stable, allowing them to persist in the environment for decades 3 .
OCPs undergo limited decomposition or degradation, remaining intact for years or even decades in the environment 1 .
These compounds have high vapor pressure, enabling them to evaporate from soil and water into the atmosphere and travel long distances 1 .
Being highly lipid-soluble, OCPs accumulate in fatty tissues of organisms and become more concentrated as they move up the food chain 3 .
The atmospheric journey of OCPs operates as a global distillation system. They evaporate in warm regions, travel through atmospheric currents, and condense in cooler regions—a process explaining how these chemicals reach Arctic ecosystems and high-altitude environments where they were never used 5 .
Scientists employ sophisticated sampling techniques to track these invisible atmospheric travelers. Both active and passive sampling methods are used to capture OCPs in their gaseous form or adhered to atmospheric particulate matter 4 . One revealing study conducted in Bursa, Turkey, between 2008 and 2009 meticulously measured atmospheric deposition of OCPs using different collection devices to understand their pathways 1 .
The Turkish research team used multiple sampling approaches simultaneously:
Collected ambient air concentrations of OCPs in both gas and particle phases 1 .
Measured dry deposition and air-water exchange fluxes 1 .
Collected both wet and dry deposition separately 1 .
Gathered bulk deposition combining wet and dry deposition 1 .
This multi-pronged approach allowed scientists to understand how OCPs move between the atmosphere and earth's surface through different mechanisms including rainfall, particle settling, and gas exchange 1 .
The year-long study revealed several important patterns about OCP behavior in the atmosphere:
The data revealed that these banned pesticides continued to circulate through deposition processes years after restrictions were implemented.
| OCP Compound | Particle Phase (pg/m³) | Gas Phase (pg/m³) |
|---|---|---|
| α-HCH | 2.10 (min) | 3.78 (min) |
| γ-HCH | 4.97 | 6.21 |
| Endosulfan beta | 73.01 (max) | 108.04 (max) |
| Deposition Type | Range | Dominant Compounds |
|---|---|---|
| Wet Deposition | 0.05-41.1 | HCHs, Endosulfans |
| Dry Deposition | 0.01-4.94 | HCHs, Endosulfans |
| Bulk Deposition | 0.11-46.0 | HCHs, Endosulfans |
| Location | Period | Total DDTs Deposition | Key Findings |
|---|---|---|---|
| Bursa, Turkey | 2008-2009 | 9.18 ng/m²/day (avg) | Wet deposition dominant for most OCPs 1 |
| US Mid-Atlantic | 1998-2000 | 0.2-33 ng/m³ (air conc.) | Highest concentrations at urban/industrial centers 8 |
| Strasbourg, France | 2018-2020 | Banned OCPs still detected | Lindane present despite ban 9 |
Modern OCP research relies on sophisticated equipment and methods:
Cost-effective devices that accumulate OCPs over time without requiring power, ideal for monitoring remote locations 9 .
Active samplers that pull large volumes of air through filters to capture particle and gas phase OCPs separately 1 .
Advanced analytical technique that separates and identifies individual OCP compounds at extremely low concentrations 7 .
Specialized containers that collect rainfall, particle settlement, and gas exchange for quantifying deposition fluxes 1 .
These tools enable scientists to detect OCPs at trace levels—sometimes as low as picograms per cubic meter—painting a detailed picture of their atmospheric transport and fate 1 9 .
The enduring presence of OCPs in our atmosphere stems from two primary sources. Primary emissions continue in some countries where specific uses remain exempt, such as DDT for malaria control in certain regions 5 . Perhaps more significantly, secondary emissions occur when OCPs deposited decades ago in soils, sediments, and vegetation re-enter the atmosphere through volatilization 5 . This creates a cycling effect where these persistent chemicals move between air, land, and water in a continuous environmental loop.
Continued use in some regions for specific applications like malaria control maintains a source of new OCPs entering the atmosphere 5 .
5 .
Recent sediment core studies from the Tibetan Plateau reveal that DDT compounds can undergo reversible transformations between different fractions in sediments, potentially prolonging their environmental half-lives far beyond initial estimates 5 . This suggests that even sequestered OCPs may remain bioavailable and capable of re-entering atmospheric circulation over prolonged periods.
The story of organochlorine pesticides in our atmosphere continues to unfold. While developed nations have successfully banned these chemicals, their persistence demonstrates how past environmental decisions echo through decades. Current research focuses on understanding the complex interplay between climate change and OCP behavior, as rising temperatures may increase volatilization and redistribution of these legacy pollutants 9 .
"The characteristics of pesticides, such as high lipophilicity, bioaccumulation, long half-life and potential of long range transport, have increased the chances of contaminating the air, water and soil, even after many years of application" 3 .
The invisible journey of these atmospheric travelers serves as a powerful reminder that what we release into our environment may travel far beyond our borders and persist long beyond our intentions.
Widespread use of OCPs begins
"Silent Spring" published
Many OCPs banned in developed countries
Stockholm Convention on POPs
OCPs still detected globally