The answer is yes and no.
DEET is a common ingredient in bug sprays and insect repellants which comes in the forms of sprays, lotions, and articles of clothing.
Research into DEET explains that it works by targeting the electrical properties of the insect’s tissues and cells that play a role in how olfactory sensory neurons (OSNs) work.
OSNs are cells that send messages between the brain and the nasal cavity.
Since the OSNs help the insect detect and transmit odorant information to the central nervous system, essentially, DEET prevents the insects from recognizing the electrical signals sent through this channel related to the odor that attracts them to us.
As we’ll discuss, the main consensus is that DEET is generally safe but has some limited effects on the environment.
What Is DEET?
DEET is a chemical compound short for N, N-diethyl-meta-toluamide. The main benefit of this chemical is as a protectant against insect bites, particularly mosquitos.
For instance, in the US, the EPA highlights DEET helps protect against insect-borne diseases such as Lyme disease, encephalitis, and West Nile virus infections.
After several reviews by the EPA, DEET has been identified as a low threat to human and environmental health when used correctly.
However, it’s worth keeping in mind that even though they say it’s a “low threat,” this doesn’t mean there are no issues.
How Does DEET Affect the Environment?
Although there’s limited evidence that DEET has an effect on the environment overall, there are some instances where DEET can be harmful.
Here are a few effects to be aware of:
1. Aquatic Environments
The effects of DEET on water have been documented in several cases.
For instance, a study found that although the risk posed by DEET to water habitats was minimal overall, when a closer inspection of its effects on some aquatic species was carried out, they noted it had negative consequences on the growth and functions of algae and several other lower-order species.
That said, it’s worth noting that these studies were conducted at a higher level of DEET toxicity than is typically present in water, at concentrations between 34 and 388 parts per million.
For context, testing for DEET concentration of water in the USA was found to be 47 parts per billion, so the study was observing toxicity at levels much higher than would be found in actual water.
The reason we mention this study, nonetheless, is because DEET use has been steadily increasing over time, which is why the researchers in the study still see these results as a point of concern.
Research like the one above and others conducted on the toxicity of DEET show that if concentration rises high enough, it can disrupt the ability of many species, not just algae, in uptaking oxygen, which could be catastrophic for aquatic species as a whole.
Moreover, since DEET has been found to affect the processes of microbial communities, it also could have knock-on effects down along the food chains.
2. Waste Disposal
As you might have guessed from above, one of the main concerns for DEET is how it is disposed of.
Generally, DEET has a very short half-life of just 5 hours when it enters the atmosphere.
In other words, we can expect it to degrade within the next day or so, and it doesn’t have a long transport range.
This is why there’s very little concern about DEET as a pollutant, as it won’t stay in the environment very long, with the EPA stating the potential for bioaccumulation or the transfer of the chemical through species is unlikely.
However, research explains it can’t be degraded in water as well as it would be in the air because it’s more resistant to degradation when it’s in liquid form.
Aquatic microorganisms can break down DEET in water, but it takes slightly longer, with a half-life of around 15 days in water and up to 135 days in sediment.
While this half-life may not be a cause for concern as DEET concentrations are low in such instances (i.e., not enough to cause harm), wastewater residue and landfill leaching from DEET can be as high as 79%, which would be sufficient to cause toxicity to algae.
As such, the environmental fate of DEET is controversial. On one hand, when disposed of properly, it should not present a risk to the environment.
But, some researchers have questioned whether this assessment of the risk that DEET poses is accurate.
Namely, since the EPA notes a lack of data on the production volume of DEET, it’s unclear as to how much DEET actually ends up in the water as a result of spills or run-off, with the final amount potentially higher than environmental studies seem to suggest.
3. Energy Consumption and Emissions
While the release of DEET itself is not known to be a pollutant, due to the vagueness surrounding its production, we can’t say for sure what kind of emissions may or may not be related to it.
The formula and process for DEET manufacturing is relatively quick, ranging between 15 to 45 minutes, which could suggest energy consumption is low.
Moreover, though the chemicals used to produce DEET, such as m-toluoyl chloride and thionyl chloride, are known to be hazardous chemicals, their dangers are localized to those working closely with the chemicals and are unlikely to have further effects on the environment.
We do know, however, that as part of the chemical and petrochemical industry, the manufacturing of DEET is at least in part contributing to the 3.6% of energy-related emissions and 2.2% related to greenhouse gasses in our current global economy.
But, this is not necessarily reflective of DEET as being environmentally bad but the industry as a whole.
4. Agricultural Effects
One aspect of DEET which is more pernicious is in its use as a pesticide.
Although DEET is said to repel insects as opposed to killing them (per the EPA), and it’s not bioaccumulative (as reported above), its presence has been detected in both honey and pollen samples in low concentrations by researchers.
This is backed up by other findings (one in simulations and another in laboratory testing) where DEET uptake by plants, most likely from the soil, was not only confirmed but said to have a degree of bioaccumulation potential in the leaves and stems of plants such as carrots and barley.
In short, there seems to be a disconnect here between reported data either in the toxicity of DEET or its ability to remain in the environment because though DEET concentrations were low, they were enough to raise concerns about the health of the bees that interact with DEET contaminated pollen and honey.
Is DEET Toxic?
The EPA and CDC seem to agree that the health effects of DEET are minimal, but there appear to be some nuances in the scientific literature as to whether this is actually true.
For instance, the EPA reports that no risks have been found through the dermal application of DEET when it is used as specified.
However, one study found that regular exposure to DEET in aerosol form could cause or exacerbate a condition called chronic rhinosinusitis (CRS).
Chronic rhinosinusitis is an inflammatory disorder of the nasal passage that lasts 12 weeks or longer.
The study remarks that farmers or people regularly exposed to DEET may be more at risk of this condition, even at relatively low exposure, suggesting that the chemical may have some cytotoxic effects – that is, it can cause cell damage.
The difference in this reporting may be because the EPAs evaluation of DEET safety only measures its effect when applied to the skin.
But of course, many DEET bug sprays are aerosols, so even when it’s applied in an open space, some particles could potentially be inhaled, leading to irritation.
Is DEET Biodegradable?
Yes, according to the CDC, DEET is biodegradable.
Microorganisms can break it down, and it’s also readily degraded in the atmosphere when it’s in gaseous form.
However, as we noted, in water, this degradation is less certain, with studies raising concerns that waste treatment for DEET is not sufficient for removal.
Especially since the vast majority (80% of DEET) ends up in the environment and aquatic systems.
Though it can be biodegraded by up to 95.64% through the application of water treatments like bleach in combination with UV radiation, the components which it’s broken down into, unfortunately, still have the potential for toxicity for aquatic species.
Are There Eco-Friendly Alternatives to DEET?
There are several eco-friendly equivalents to DEET to consider.
According to research, these plant-based species are effective at repelling mosquitoes for several hours and can serve as an inexpensive alternative to chemical insect repellants:
- Citronella is an essential oil derived from lemon grass. The research found it was the most effective at repelling mosquitos and could offer protection for up to 8 to 14 hours.
- H. suaveolens is another essential oil derived from pignut, which comes from the lavender family. A study found it was similarly effective to DEET with a six-hour protection time.
Other repellents of note include:
- Ligusticum sinense (wild parsnip) extract, pine, Dalbergia sissoo (Indian Rosewood), and Rhizophora mucronata (a species of mangrove) oils also had a similarly high efficacy, offering protection for up to 8 hours.
- Lavender, geranium, jasmine, cedarwood, chamomile, cinnamon oil, juniper, and rosemary showed a slightly lower but still significant efficacy of around 90% against mosquitoes for up to 8 hours.