Boric acid

Boric acid is a compound of boron, oxygen, and hydrogen. It may also be called hydrogen orthoborate, trihydroxidoboron or boracic acid. It is a weak acid that yields various borate anions and salts, and can react with alcohols to form borate esters. Boric acid is often used as an antiseptic, insecticide, flame retardant, neutron absorber, or precursor to other boron compounds.

Orthoboric acid was first prepared from borax, by the action of mineral acids. Boric acid and borax are closely related compounds derived from boron, a naturally occurring element. Borax, also known as sodium tetraborate decahydrate (Na₂B₄O₇·10H₂O), is a mineral salt mined from boron-rich deposits, while boric acid (H₃BO₃) is a weaker acid produced by reacting borax with a strong acid, such as hydrochloric or sulfuric acid, in a process that releases boron-oxygen compounds and water. Both substances share similar chemical properties due to their boron content and are used as antiseptics, insecticides, and cleaning agents, but boric acid is more acidic and typically used in applications requiring a milder, less alkaline compound, such as pest control or medicinal uses, whereas borax is more commonly used in household cleaners and laundry boosters. Their relationship stems from borax serving as a primary source material for manufacturing boric acid, linking them through both chemistry and practical applications.

insecticide effectiveness

Boric acid is a great insect control solution due to its effectiveness and low risk to humans and pets when applied judiciously (e.g., in baits or inaccessible areas).

• Use boric acid in enclosed baits or apply it sparingly in areas pets and children can’t access.
• Avoid loose powder in open spaces to prevent inhalation or ingestion.
• Monitor pets for grooming in treated areas.

Boric acid is highly effective against insects like cockroaches, ants, and silverfish, acting primarily as a stomach poison when ingested. It disrupts insects’ digestive and nervous systems, with a slow-acting nature that allows pests to carry it back to colonies, enhancing its impact (as noted in pestideas.com and Hacker News). Its efficacy is maximized in dry environments and when combined with attractants in baits. However, it’s less effective against pests like bed bugs or beetles that don’t readily ingest it. Compared to diatomaceous earth, boric acid is less messy and easier to apply in targeted areas, making it a practical choice for home pest control.

Boric acid was first registered in the US as an insecticide in 1948 for control of cockroaches, termites, fire ants, fleas, silverfish, and many other insects. It is in non-specific IRAC group 8D. Boric acid is also known as "the gift that keeps on killing" because cockroaches cross over lightly dusted areas and do not die immediately. Still, the effect is like shards of glass cutting them apart. This often allows a cockroach to return to the nest, where it soon dies. Cockroaches, being cannibalistic, eat others killed by contact or consumption of boric acid, consuming the powder trapped in the dead roach and killing them.

Boric acid is also widely used in wood treatment to protect against termites. Aside from causing dose-dependent mortality, boric acid causes dysbiosis in the Eastern Subterranean termite, leading to the opportunistic rise of insect pathogens that could be contributing to mortality. In combination with its use as an insecticide, boric acid also prevents and destroys existing wet and dry rot in timbers. It can be used in combination with an ethylene glycol carrier to treat external wood against fungal and insect attack.

mice and rats

Boric acid is ineffective against these pets. Boric acid is ineffective as a rodenticide for mice and rats because they are unlikely to ingest boric acid in sufficient quantities because it is not inherently attractive to them. Unlike insects, which may consume boric acid mixed with baits, rodents are more selective feeders. Boric acid is not palatable to rodents without highly effective baiting strategies, and even then, they may avoid it due to its taste or lack of appeal compared to other food sources.

Boric acid works primarily as a stomach poison for insects, requiring ingestion to disrupt their digestive and nervous systems. For rodents, achieving a lethal dose through ingestion is challenging because they would need to consume a large amount relative to their body weight, which is unlikely under normal conditions. Professional pest control resources, such as those from the National Pesticide Information Center, confirm that boric acid is primarily registered for insect control (e.g., cockroaches, ants) and not for rodents.

safety to pets and humans

Boric acid, when used as a pest control agent in the home, is generally considered relatively safe for humans, cats, and dogs if applied correctly and ingestion is avoided, particularly in large quantities. Its low toxicity makes it a popular choice for controlling insects like roaches and ants, but precautions are necessary to minimize risks from dust exposure or accidental ingestion.

• Boric acid has a low acute toxicity for mammals. For humans, the lethal dose is estimated at 15–20 grams for adults and 2–3 grams for infants, far higher than typical exposure levels from pest control use. For dogs and cats, similar principles apply—small amounts are unlikely to cause harm, but large doses can be toxic.
• The primary concern is ingestion. Pets, especially cats (who groom themselves) or dogs (who may lick surfaces), could ingest boric acid if it’s applied in areas they access. Symptoms of toxicity include vomiting, diarrhea, lethargy, and, in severe cases, neurological issues or kidney damage. Chronic low-level ingestion over time can also accumulate and cause problems.
• Boric acid dust, when applied as a powder, poses a minimal risk if inhaled occasionally in small amounts. However, prolonged or heavy exposure to airborne dust can irritate the respiratory tract or eyes in humans and pets. Proper application (e.g., in thin layers in hard-to-reach areas) reduces this risk.
• Occasional skin contact with boric acid is not considered hazardous for humans or pets. It’s not readily absorbed through intact skin, and studies show minimal irritation unless exposure is prolonged or the skin is broken. However, pets grooming themselves after contact could ingest small amounts, so contact should be minimized.

To ensure boric acid is safe for home use around pets and people you should apply Sparingly in Inaccessible Areas. Place boric acid in cracks, crevices, or behind appliances where pests travel but pets and humans are unlikely to contact it. Avoid open surfaces like floors or countertops. Young children are more vulnerable due to hand-to-mouth behavior and lower body weight. Ensure treated areas are inaccessible to them.

You can set up bait stations. Enclosed bait stations containing boric acid reduce the risk of pet or human exposure compared to loose powder. Try to keep pets away from treated areas during application and until dust settles. Watch for signs of grooming in treated areas. Ensure good ventilation when applying to minimize inhalation of dust. Keep boric acid containers out of reach of pets and children to prevent accidental ingestion.

For cats and dogs, the relative harmlessness of boric acid holds true as long as exposure is minimized:

• Cats: Cats are more vulnerable due to their grooming behavior and lower body weight. However, small amounts on fur or paws are unlikely to cause harm unless grooming leads to significant ingestion over time. Avoid applying boric acid in areas where cats might walk or rest.
• Dogs: Dogs are less likely to groom excessively and have higher body weights, reducing risk. House Digest confirms that boric acid is safe around dogs when applied in inaccessible areas or baits.

Regulatory and Expert Guidance: The U.S. Environmental Protection Agency (EPA) classifies boric acid as a low-toxicity pesticide for household use when applied according to label instructions. Veterinary sources, like the ASPCA, note that small exposures (e.g., walking through treated areas) are unlikely to cause serious harm, but ingestion of concentrated amounts (e.g., from a spilled container) requires immediate attention. The National Pesticide Information Center emphasizes that proper application is key to safety.

In summary, boric acid is relatively safe for pest control in homes with pets and people if used judiciously, avoiding ingestion and minimizing dust exposure. Occasional skin contact or brief exposure to settled dust is not a significant hazard, but careful application and monitoring are essential to prevent accidental ingestion, especially by pets. If you’re concerned about specific risks or have sensitive pets, consult a veterinarian or pest control professional for tailored advice.

food preservative

Boric acid was used in the late 19th and early 20th centuries as a preservative in meat, including sausages, often by unscrupulous butchers and meat processors to mask spoilage and extend shelf life. This practice was particularly prevalent in urban areas where demand for cheap food was high, and impoverished communities were frequent targets for such adulterated products. Boric acid, derived from boron, slowed decomposition by reacting with proteins, giving rotting meat a firmer, more appealing appearance, and was sometimes used to disguise off odors and textures. Its use was widespread because it was cheap and effective, despite growing concerns about its safety.

Historical records indicate that boric acid was a common food preservative during this period, not only in meat but also in butter and milk. For example, it was implicated in the "embalmed beef" scandal during the Spanish-American War (1898), where meat treated with boric acid and other chemicals was supplied to U.S. soldiers, leading to illness and public outrage. The chemical’s ability to mask spoilage made it attractive to unethical vendors aiming to sell substandard meat to unsuspecting consumers, particularly in lower-income areas where buyers had fewer options.

Public health advocates, notably Dr. Harvey Washington Wiley, Chief Chemist of the U.S. Department of Agriculture, exposed these practices through experiments like the "Poison Squad" (1902–1907). These trials tested the effects of preservatives like boric acid on human volunteers, revealing health risks such as digestive issues and potential toxicity. Wiley’s work, combined with public outcry and exposés like Upton Sinclair’s The Jungle (1906), which detailed unsanitary meatpacking practices, fueled the push for regulation.

The U.S. government responded with the Pure Food and Drug Act and the Meat Inspection Act of 1906, which established federal oversight of food safety and banned harmful preservatives, including boric acid, in food products. These laws marked a turning point, outlawing the use of boric acid and similar substances in meat processing due to their health risks and deceptive applications. In the UK, similar concerns led to earlier food safety laws, like the Adulteration of Food and Drink Act of 1860, with further regulations in the early 20th century tightening controls on preservatives.

While boric acid was not universally used by all butchers, its application by unscrupulous ones was well-documented before government intervention. The practice declined significantly after 1906 in the U.S. and similar periods in other countries as regulatory enforcement and public awareness grew.