Side Effects of Herbicides

Herbicides are used to kill weeds and other undesirable plants. There are many different types of herbicides, all of which can be dangerous to humans or the environment if used irresponsibly. Paraquat, atrazine and Agent Orange are among the most well-known herbicides, but there are many others. Herbicides may cause harm by acute poisoning or long-term, cumulative exposure, with side effects ranging from mild to deadly. Understanding the side effects of herbicides can help to prevent unnecessary harm if you are exposed to these substances.

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If you are experiencing serious medical symptoms, seek emergency treatment immediately.

Respiratory Damage

When inhaled, many herbicides can cause serious damage and irritation to the respiratory tract. The nose, throat, lungs and sinuses may be affected, causing either temporary symptoms or permanent structural damage. According to Medline Plus, paraquat—a toxic herbicide applied to illegal drug crops in the 1970s and 1980s—can cause nosebleeds, throat burns and acute respiratory distress syndrome. In severe cases, it may even burn holes in the esophagus or lead to pulmonary fibrosis, a permanent lung disease.

Severity of respiratory symptoms caused by paraquat depends largely on the length and amount of exposure. Swallowing paraquat, even in small amounts, often leads to death, according to Medline Plus.


While it can be difficult to determine the true cause of cancer in most cases, certain herbicides have been linked to an increased risk for cancer in humans. Agent Orange—a defoliant used in the Vietnam war—is among the most notorious herbicides in history, being implicated as a possible cause of birth defects, cancer and a host of other health problems 2.

A study by Sagar Shah and colleages featured in the March 6, 2009 edition of BJU International states that the dioxins contained in Agent Orange may increase the risk for developing a type of prostate cancer that is more virulent and harder to treat than many other forms of the disease.

Birth Defects

Some herbicides may increase the risk for birth defects in unborn children. As with cancer, specific birth defects may be difficult to link to herbicides. According to the BBC News, babies exposed to Agent Orange in the womb are more than three times as likely to suffer from mental retardation, cleft palate and other birth defects, such as the presence of extra fingers or toes 2.

Environmental Effects

While most herbicides are not considered dangerous to animals, all pose a potential risk for causing adverse environmental effects. By changing the availability of nest sites and disrupting an animal’s food source, herbicides may make it difficult for some species of birds, insects and other creatures to survive.

Endangerment and extinction of species are among the greatest risks of herbicide use, though they are usually associated with extensive use over a long time.