Tag Archives: herbicide

Agent Orange continues to pollute Vietnam environment, study finds

A “tactical” herbicide used by the US army during the Vietnam War is still affecting the environment and the people relying on it.

The Vietnam government has set up programs to reforest areas heavily affected by Agent Orange. You can clearly see the affected forest line here. Image credits: a_brinr.

“The soils, tropical climate, and network of canals and rivers of southern Vietnam have created one of the most diverse tropical jungles and intensely cultivated landscapes of Southeast Asia,” researchers start off in their study. But, as they continue explaining, it’s also one of the most war-torn areas in modern history. “This paradise has a long history of
numerous wars, foreign occupations, and most recently the Second Indochina War (aka the Vietnam War 1965-1972) which defoliated rain forests and ancient wetland mangroves and left behind contaminated soil and sediment hotspots.”

The Vietnam War was a brutal and unrestrained affair, costing the lives of over 1,000,000 soldiers, and even more civilian casualties. The number of serious injuries it inflicted lied in the millions, and to this day, the area is still recovering. The environment, researchers note, is also still recovering.

In order to be able to operate better in the luxuriant Vietnamese vegetation, the US military deployed a “tactical herbicide”, which became popularly known as Agent Orange. Over 20 million gallons (90 million liters) of Agent Orange were poured over Vietnam’s rainforests, wetlands, and croplands. It defoliated the vegetation, destroyed a significant part of the food crops, and exposed over 4 million people to the harmful effects of the herbicide.

The Vietnam government estimates that as many as 3 million people have suffered illnesses because of Agent Orange, and the Red Cross notes that over 1 million people were left disabled or suffering severe health issues due to exposure. Environmental damage was also huge. In a new study, researchers wanted to assess just how much damage Agent Orange is still causing.

“Existing Agent Orange and dioxin research is primarily medical in nature, focusing on the details of human exposure primarily through skin contact and long-term health effects on U.S. soldiers,” says Ken Olson, professor emeritus in the Department of Natural Resources and Environmental Sciences at University of Illinois and co-author on the article. “In this paper, we examine the short and long-term environmental effects on the Vietnamese natural resource base and how persistence of dioxin continues to affect soils, water, sediment, fish, aquatic species, the food supply, and Vietnamese health.”

US aircraft sprayed 20 million gallons of herbicides across Vietnam during the Vietnam War. Dioxin, a contaminant in Agent Orange, persists today. Image credits: US Army Flight Operations Specialist 4 John Crivello in 1969.

Agent Orange is an equal mixture of two herbicides, 2,4,5-T and 2,4-D, both of which have been noted to be hazardous to human health at significant quantities. The first one was effectively banned in the ’80s, and the second one has been heavily regulated ever since. In theory, neither of the two can last for too long in nature — they tend to disintegrate after a few weeks when exposed to sunlight. However, when they were combined, they produced a dangerous by-product: dioxin TCDD, the most toxic of the dioxin family of chemicals. As it seeps into the soils and plants, TCDD can stick around for decades or even centuries.

Essentially, TCDD attaches itself to organic molecules and clay and clings on to them.

“The pathway begins with the U.S. military spraying in the 1960s, absorption by tree and shrub leaves, leaf drop to the soil surface (along with some direct contact of the spray with the soil), then attachment of the dioxin TCDD to soil organic matter and clay particles of the soil,” says Lois Wright Morton, also a study author.

The team found that TCDD moved around in surface runoff — as the sediment particles were moved around, TCDD went with them. Often, it settled into humid areas like wetlands, marshes, or lakes. From there, it ended up ingested by fish and shrimp, accumulated inside their tissues, and moved up the food chain. Although fishing is technically banned in contaminated areas, the bans have been difficult to enforce, and people still end up ingesting TCDD-contaminated fish. Even 50 years later, new generations are still suffering the effects of TCDD contamination, researchers say, with no clear end in sight.

Researchers mapped the 10 airbase sites where dioxin TCDD is believed to persist at the highest levels. Millions of Vietnamese live in adjacent cities and villages and are exposed to dangerous levels of contamination.

“The worst dioxin-contaminated site in Vietnam is Bien Hoa airbase, which is 30 miles north of Ho Chi Minh City,” Olson says. “After President Nixon ordered the U.S. military to stop spraying Agent Orange in 1970, this is the site where all the Agent Orange barrels remaining in Vietnam were collected. The barrels were processed and shipped to Johnston Island in the Pacific Ocean, where they were incinerated at sea in 1977.”

There are two main approaches to dealing with this contamination. The cheapest — and only one used at a large scale — is landfill storage. However, instead of truly dealing with the problem, this only offers temporary storage, delaying the contamination rather than eliminating it. Researchers suggest another approach: incineration.

It’s a lengthy and costly process, but incinerating contaminated sediments is the only realistic way of dealing with the contamination, researchers conclude.

“While incineration is the most expensive technology currently available, it would eliminate dioxin rather than temporarily store it in a landfill, and incineration would not require future maintenance or treatment. Incineration is one of the most commonly used technologies, having been used to treat soils at more than 150 superfund sites, and is a mature and tested technology,” the authors say.

This serves as yet another reminder of how devastating and long-lasting the consequences of modern war can be. Even 50 years later, the “tactical herbicide” is still doing its job, affecting Vietnam’s environment and human population.

Journal Reference: Kenneth Ray Olson, Lois Wright Morton. Long-Term Fate of Agent Orange and Dioxin TCDD Contaminated Soils and Sediments in Vietnam Hotspots. Open Journal of Soil Science, 2019; 09 (01): 1 DOI: 10.4236/ojss.2019.91001


Glyphosate might be killing bees by messing with their gut bacteria


Credit: Pixabay.

Glyphosate, a broad-spectrum herbicide, has been in wide use since the 1970s with farmers looking to control weeds. Its manufacturer, Monsanto, has always claimed that the chemical only affects plants, being harmless to animals. A new study, however, shows that Glyphosate may be indirectly killing bees by disrupting the microbial community living in their digestive system. As such, the most popular herbicide in the world may be another important factor contributing to the alarming decline in bee populations all over the globe.

“We need better guidelines for glyphosate use, especially regarding bee exposure, because right now the guidelines assume bees are not harmed by the herbicide,” said Erick Motta, a graduate student at the University of Texas Austin, who led the research. “Our study shows that’s not true.”

Glyphosate is a non-selective herbicide, meaning it will kill most plants — including crops and weeds. It works by blocking a specific enzyme, the shikimic acid pathway, which prevents the plant from making key proteins required for growth. The shikimic acid pathway is not found in animals, which is why glyphosate is deemed non-toxic to humans.

However, the enzyme is used by some bacteria. Researchers at the University of Texas in Austin wondered whether glyphosate might be affecting bacteria strains living in the intestines of honey bees (Apis mellifera). They collected 2,000 bees from a hive and fed them sugar syrup dosed with herbicide levels they might encounter in real life.

Three days after they returned to their hives, the glyphosate-exposed bees had fewer Snodgrassella alvi bacteria in their guts than those which were not exposed. Confusingly, the bees that got the highest dose of glyphosate had a microbiome closer to optimal levels compared to bees that received the lowest dose of the herbicide. The researchers say that this may be due to the fact that bees with the highest dose died, leaving behind the resistant variety.

Things become clearer in later tests that showed that glyphosate-laden bees had five times less of the S. alvi bacterium. And when the researchers cultured the bacteria in a petri dish, its growth was very slow or stopped altogether when exposed to a high dose of glyphosate.

Writing in the Proceedings of the National Academy of Sciences, the authors suspect that changes in the bee’s microbiome make the bees more vulnerable to infections. Only 12% of the bees fed with glyphosate survived an infection from Serratia marcescens compared with 47% that were not fed glyphosate. S. marcescens is a bacteria that is widely found in beehives and bee guts that can invade other parts of a bee’s body, leading to lethal infections.

“Studies in humans, bees and other animals have shown that the gut microbiome is a stable community that resists infection by opportunistic invaders,” Moran said. “So if you disrupt the normal, stable community, you are more susceptible to this invasion of pathogens.”

S. alvi lines part of the gut wall and, as such, could act as an insulating layer against the potentially lethal S. marcescens. Additionally, S. alvi also secrets a chemical that can disrupt the invading bacterium.

The findings offer an alternative explanation for the massive decline in bee populations seen all over the world. For instance, beekeepers in the U.S. lost 42.1 percent of their bee colonies in just one year, between April 2014 and April 2015.

“Since the 1980s, honeybees and beekeepers have had to deal with a host of new pathogens from deformed wing virus to nosema fungi, new parasites such as Varroa mites, pests like small hive beetles, nutrition problems from lack of diversity or availability in pollen and nectar sources, and possible sublethal effects of pesticides, ” the USDA notes. But deaths began to spike in the middle of the past decade, when a phenomenon in which bees deserted their hives and died en masse – later named colony collapse disorder – began sweeping hives worldwide. “Commercial keepers were particularly prone to summer losses.”

Previously, scientists have linked colony collapse disorder (CCD) with pesticides, habitat loss, climate change, parasites, stress, and lack of flowers. In this constellation of stressors threatening the most important pollinators on the planet, glyphosate may also pose an important risk.

“It’s not the only thing causing all these bee deaths, but it is definitely something people should worry about because glyphosate is used everywhere,” said Motta.

The findings also raise some important questions about glyphosate’s safety. Perhaps it is affecting the microbiome of other animals, including humans. Previously, the science has been conflicting in its assessment of whether the chemical is carcinogenic or not.

Monarch butterfly populations went down 80% in 21 years

A new study has found that monarch butterfly populations have dwindled at alarming rates in the past couple of decades, dropping on average by 80%. In the forests of Mexico, they went down by as much as 90%.


The monarch butterfly (Danaus plexippus) is known for its annual southward migration from Canada and the US to Mexico, which takes several generation. Usually, the initial populations overwinter in various coastal sites in central and southern California. The overwintered population of those east of the Rockies may reach as far north as Texas and Oklahoma during the spring migration. The second, third and fourth generations return to their northern locations in the United States and Canada in the spring.

However, in recent times, their populations have been going down dramatically – and the main cause, as usually, is us – our pesticide use, to be more precise.

The main food source of these butterflies is milkweed, also an important nectar source for native bees, wasps, and other nectar-seeking insects. The increasing usage of pesticides for agriculture has led to a decline in milkweed habitats.

“A monarch that leaves its wintering grounds in Mexico will never make it to Vermont,” said Mark Ferguson, a biologist with the Vermont Fish and Wildlife Department, in an interview with The Boston Globe. “Instead, several generations are born and die along the way, meaning that the grandchildren or great-grandchildren of the monarchs leaving Mexico eventually arrive in Vermont each summer. Because monarchs need milkweed to reproduce, anything we can do in Vermont to promote this vitally important species will help monarchs thrive.”

Ferguson believes that Vermont will play a key role in the future of monarchs, because its meadows and old fields provide habitat for milkweed. This means that if officials support the re-expansion of milkweed, the butterflies could be saved. Ferguson has recommended that people should limit the use of insecticides and herbicides to the strict necessary.

Bonus Fact: Monarchs are foul-tasting and poisonous due to the presence of a specific type of steroids in their bodies, which the caterpillars ingest as they feed on milkweed.