September 15, 2025 › Big Chemical › Health Conditions › News
Toxic Exposures
Research published this week in Environmental Science & Technology is the first to detect dozens of agricultural chemicals — including insecticides, herbicides and fungicides — suspended in clouds above France. The pollutants eventually fall back to Earth in rain or snow, sometimes at levels exceeding European safe drinking water limits.
September
15, 2025
3833 Pageviews
By Pamela Ferdinand
Key findings:
·
Pesticides — including 10 banned in the European Union (EU) due to
health concerns — were detected in every cloud sample above France.
·
Two samples exceeded Europe’s drinking water safety limit.
·
Clouds
carried not just pesticides but also emerging contaminants and new breakdown
products.
·
Most
pollution came from long-range pesticide drift, not local farms.
·
At any given
time, French clouds may hold 6 to 139 tons of pesticides.
Pesticides banned years ago in the EU are drifting through the skies and turning up in clouds above France, raising concerns about how long these toxins persist and how far they can travel, with potentially harmful global health impacts, according to a pathbreaking new study.
The research, published on Sept. 8 in Environmental Science & Technology, is the first to detect dozens of agricultural chemicals — including insecticides, herbicides, fungicides and other substances — suspended in cloud water droplets.
That means pesticides not only linger in the environment but also move through the
atmosphere and fall back to Earth in rain or snow, sometimes at levels
exceeding European safe drinking water limits, the research suggests.
Clouds, once seen as passive carriers of water, are now recognized as
active players in chemical transport and transformation, with direct
implications for ecosystems, drinking water and public health.
“Pesticide contamination is a growing and alarming concern for both the
environment and human health,” the researchers say.
“Widely used in agriculture to control pests and disease carriers,
pesticides undergo extensive long-range atmospheric transport in the gas phase,
in aerosols, and, as shown here, in clouds.”
The implications for public health are stark, especially at a time
when agricultural pesticide
use has increased
dramatically and the industry continues to
shape pesticide policy in the
U.S. and elsewhere.
Most recently, the Make America Healthy
Again Commission report,
under the Trump administration, advanced industry priorities by backpedaling on pledges to reduce pesticide use.
Pesticides such as atrazine have been linked to a wide range of potential harms. They
include childhood and
adolescent cancers,
neurological disorders and a range of reproductive, respiratory, metabolic and
developmental problems, from infertility and premature birth to Parkinson’s disease and Type 2 diabetes.
The study found that clouds can carry current-use pesticides,
long-banned compounds and “emerging contaminants” — industrial chemicals that either build up in the environment or form
when older pesticides break down.
Some even transform
into new compounds in the atmosphere itself, beyond what regulators have known
to consider.
Researchers
estimate that French skies alone may contain anywhere from a few tons to more
than 100 tons of pesticides at any given time — most carried in from distant
sources.
With pesticide use continuing worldwide, they argue, the problem extends
well beyond national borders and local farming practices.
Clouds as unexpected reservoirs of toxic chemicals
This is the first time scientists say they have directly measured such a
large number of pesticides in cloud water high in the atmosphere — well above
the immediate influence of local farms. Clouds contain tiny liquid droplets
that can trap pollutants like pesticides and later deliver them back in the
form of rain or snow.
Clouds also act as chemical “reactors.” The study found that they not
only transport pollutants but also transform them into other substances.
An upcoming study by some of the same researchers shows, for instance,
that triphenyl phosphate, a toxic chemical used in plastics and flame retardants, turns into
other chemicals, including diphenyl phosphate, in about 90 minutes in cloud
water.
To capture the data, the researchers collected
cloud water samples during late summer 2023 and spring 2024 at Puy de Dôme, a
mountaintop observatory and research station in central France, which is
uniquely positioned to study the chemistry of the free troposphere (the part of
the atmosphere above local ground-level influences).
The site is part of European and global monitoring networks, including
Aerosols, Clouds and Trace Gases Research Infrastructure (ACTRIS) and the World Meteorological
Organization’s Global Atmosphere Watch.
Out of 446 possible chemicals screened — including pesticides, biocides
(compounds that kill harmful organisms), additives and transformation products
(breakdown products of pesticides) — researchers
found 32 different compounds in cloud water.
The list included:
·
Herbicides (9) –
weedkillers.
·
Insecticides (7) –
chemicals targeting insects.
·
Fungicides (3) – used against crop fungi.
·
Biocides (1) –
agents that kill harmful organisms.
·
Additives (3) – ingredients added to pesticide formulations.
·
Transformation products (8) – byproducts formed as pesticides degrade.
Cloud water also
contained “emerging contaminants,” including:
·
Anthraquinone, a bird repellent that is also
formed during combustion and from the degradation of polycyclic aromatic
hydrocarbons in the atmosphere, appeared in every sample (up to 93 nanograms
per liter or ng/L).
·
Benzotriazole, used in fungicide production and
widely in plastics and detergents, appeared in four samples. Although it is an
intermediate chemical in fungicide production, it is also commonly used in
other industries as an anticorrosive, plastic stabilizer and detergent
additive. Because of its broad use, it has already been detected in snow,
aerosols and surface and groundwater.
·
2,4-dinitrophenol, a volatile chemical once classified as a pesticide by the U.S.
Environmental Protection Agency (EPA) that has since been banned. Listed as a
priority pollutant, it was found in four cloud water samples at concentrations
up to 2 micrograms per liter (μg/L) — much
higher than the drinking water limit established by the EU.
Pesticide levels were higher in late summer than in
spring, with half the samples exceeding 0.5 μg/L — the European drinking water
limit for all pesticides combined, the researchers say.
Even when
2,4-dinitrophenol, which can form through photochemical reactions, was
excluded, two cloud samples still surpassed that threshold.
Some detections involved chemicals still authorized
in France. For example, the herbicide mesotrione reached concentrations up to 620
ng/L, while the insect repellent DEET appeared at 63 ng/L.
But 10 of the detected compounds were active ingredients or metabolites
of pesticides banned in the EU. They included atrazine (banned in 2003), carbendazim (2008)
and insecticides such as DNOC, fipronil, karbutilate and permethrin. Also
identified were the fungicide tolylfluanid (2022) and a breakdown product of
amitraz (2004).
The herbicide metolachlor — banned in France
after being linked to widespread groundwater contamination — was detected in
three cloud samples, even though its successor, S-metolachlor, was banned mere months after sampling.
Researchers say the
presence of these older, unauthorized compounds underscores the role of
long-range atmospheric transport: Chemicals
may be drifting into France from other countries, where they remain in use.
“The presence of
pesticides in cloud water suggests the importance of in-cloud washout [the
process by which pollutants are absorbed in cloud droplets], where they can be
present and transported,” the researchers say.
“Moreover, it raises the question
on the environmental and toxicological impact of pesticide transformation in
the aqueous phase of clouds, as already observed for other anthropogenic
[human-made] and biogenic [naturally occurring] compounds.”
Tracking the drift: How pesticides
reach the skies
Where the air came
from mattered. The most contaminated cloud samples had passed over cropland
during peak spraying seasons.
One late-summer
sample, for instance, originated over the Atlantic Ocean but crossed western
France, accumulating pesticides along the way. It contained 1.45 μg/L of total pesticides — nearly three times the EU
drinking water limit.
Another sample, traced partly to Spain and French farmland, also showed
high concentrations. By contrast, spring samples showed much lower levels
because their air masses spent most of their time over the Atlantic Ocean or
forests.
Two intermediate samples picked up pesticides while traveling over
croplands in France and Ireland.
Local sources played little role. Only one sample spent more than 5% of
its time near the mountaintop research observatory itself, and the “chemical
fingerprint” in the clouds differed sharply from nearby rivers and streams,
which were dominated by metolachlor and its breakdown product metolachlor-ESA.
Local waterways contained little or no contamination, confirming that
the pesticides found in clouds were not due to nearby spraying.
Comparisons with past studies of aerosols (tiny airborne particles)
added another dimension. Dozens of pesticides have been found in aerosols across Europe, especially near farmland. At Puy de Dôme, however, only eight
overlapped with cloud detections.
Two pesticides —
fipronil and cypermethrin — were found only in clouds, suggesting that cloud
droplets capture and retain chemicals differently than dry airborne particles.
The comparison also highlighted how pesticides may chemically change
inside cloud droplets.
Several pesticide transformation products, including breakdown compounds
of tolylfluanid, fipronil, amitraz, prothioconazole and terbutylazine, appeared
in clouds but not in aerosols.
Public health is at stake, especially
for children
Globally, about 2.6 million metric tons of active pesticide ingredients
are used each year. When sprayed on fields, as much as half can drift into the
air immediately through wind or evaporation.
Many are semi-volatile organic compounds, able to shift between liquid,
solid and gas states. This allows them to cycle repeatedly through the
atmosphere in a process known as the “grasshopper effect”— evaporating, traveling long distances, settling back to Earth and then re-evaporating again.
Recent studies have also found a wide range of pesticides in the air:
older organochlorine insecticides like dichlorodiphenyldichloroethylene (DDE,
the breakdown product of banned DDT) and endosulfan, organophosphates such
as chlorpyrifos and diazinon, and modern herbicides and fungicides like glyphosate and chlorothalonil.
Many appear in PM2.5 — fine airborne
particles of 2.5
micrometers or less that can penetrate deep into the lungs.
The EU’s SPRINT project (2020-2025) also found pesticides virtually everywhere — soil,
water, crops, dust and even in people — often as chemical mixtures or “cocktails.”
These mixtures sometimes included banned substances and usually produced
more potent effects than single chemicals, especially in sensitive species such
as earthworms or laboratory mammals. That project concluded that real-world
exposures are more complex and hazardous than regulations currently recognize.
The health risks are clear.
Pesticides can settle into homes, playgrounds, sports fields, nature
reserves and urban spaces, where they contribute to chronic exposures already
occurring through water, soil and food.
Children, whose bodies are still developing, are especially vulnerable
to pesticide exposure, and people living or working near farms face the most immediate risks.
But the French cloud study shows that no
one is entirely protected.
Meanwhile, in the U.S., pesticide regulation remains looser than in Europe. Regulators address pesticides individually, and most are exempt from
drinking water rules unless specifically limited by the EPA.
Unlike Europe, the U.S. has no overall cap on the total concentration
of pesticides in drinking
water, and industry lobbying has also weakened reform efforts.
The researchers in this new study suggest their findings are a wake-up call. In their most polluted sample, clouds could hold about 139 tons of
pesticides — roughly 0.2% of France’s annual pesticide use. Other samples
ranged from just under 4 tons to more than 110 tons.
Cloud tops
varied from 2 kilometers over Normandy to as high as 9 kilometers over eastern
France, showing that pesticides can be distributed across multiple layers of
the atmosphere.
The
researchers caution that these are
rough estimates from a single site on single days, but they stress that the quantities are significant
enough to warrant urgent attention.
In France, with
clouds of varied origin, the pesticide concentration is not the same throughout
the air column, they say. That could mean there is more in some regions and
less in others, but more research is needed.
“These results
provide the first estimate of the pesticide quantity in cloud water, which may
be significant,” the study concludes. “They stress the need for further
measurements of pesticides in the cloud.”
Originally published by U.S. Right to Know.
Pamela Ferdinand is an award-winning
journalist and former Massachusetts Institute of Technology Knight Science
Journalism fellow who covers the commercial determinants of public
health.
Categories: Air
Pollution, Big
Chemical, Health
Conditions, Herbicides/Pesticides, Toxic
Exposures, Water
Pollution
Tags: Big
Chemical, Children's
Health, Glyphosate
- Roundup, MAHA -
Make America Healthy Again, Pesticides
- Herbicides, Pollution
- Air, Pollution
- Wate
Source :
https://childrenshealthdefense.org/defender/toxic-skies-clouds-toxic-pesticides-rain-down-earth-rtk/
------------------------
Are Clouds a Neglected Reservoir of Pesticides?
- PMID: 40920485
- DOI: 10.1021/acs.est.5c03787
Abstract
Pesticide contamination is a growing and alarming concern for both the environment and human health. Widely used in agriculture to control pests and disease carriers, pesticides undergo extensive long-range atmospheric transport in the gas phase, in aerosols, and, as shown here, in clouds. We measured the concentration of 32 pesticides at the puy de Dôme observatory (France) in the sub μg L-1 to μg L-1 range in cloud water, largely arising from regional to long-range transport that also involves pesticides currently banned for agricultural use in France. Half of the samples showed a total concentration of pesticides of over 0.5 μg L-1, which is the European drinking water limit. If 2,4-dinitrophenol, which can also be produced by photochemical reactions, is excluded, two samples still present a total concentration of over 0.5 μg L-1. The frequent detection of pesticides in rainwater may thus depend on their presence in clouds as well as atmospheric washout. Estimates of pesticides' quantity in clouds over France, ranging from 6.4 ± 3.2 to 139 ± 75 tons, suggest that their amounts in the cloud aqueous phase are potentially high and that these compounds would affect areas that are not directly impacted by agricultural activities.
Keywords: cloud water; long-range transport; pesticides; puy de Dôme.
