Do Potted Plants Produce VOCs in Your Home?

I have written extensively showing that plants do not clean the air in your home, and now new studies suggest that they actually produce VOCs that pollute the air. Not only that, but plastic pots and microbes in the soil make the problem even worse.

Should you get rid of your houseplants to have cleaner air in your home and office?

What are VOCs

This is a large class of compounds that have a fairly general definition. VOCs are organic chemicals (i.e. contain carbon) that have high volatility which means they easily convert from a solid or liquid into a gas at room temperature. Humans may or may not be able to smell them, but you are familiar with many that have an odor, including pain thinner, perfume, the smell of a rose, the forest smell after a rain and the smell of pine needles.

In popular literature the term VOC tends to be used to describe harmful chemicals such as benzene, which is a carcinogen. The online discussions that incorrectly credit plants for removing VOCs from the air in our homes are mostly focused on such harmful VOCs.

The reality is that VOCs may or may not be harmful to other forms of life. Many are biologically inactive, or exist in such low levels that they are not a concern.

Reports of Plants Producing VOCs

In the last few years some popular gardening blogs have written articles about plants producing VOCs. One rather crafty title is, “Bad Green: Some Indoor Plants Release Volatile Organic Compounds“. The aim of the title is to worry people about toxic compounds but that ignores the real facts.

The science that is being reported in these posts was published in 2009 but in the gardening world it is current news. The study looked at 4 common houseplants including peace lily, snake plant, weeping fig and areca palm. Each species produced a different number VOCs, with the peace lily winning at 23 different compounds.

The message in gardening circles is clear; houseplants produce toxic VOCs. But is that the truth?

Do Plants Produce VOCs?

Absolutely. Plants produce hundreds to thousands of volatile organic compounds that are used in many ways.

Fragrant Flowers

The fragrance of flowers are due to VOCs. We select plants for this quality but the real reason plants produce these compounds is to attract pollinators.

Waning About Pests

When a bug chews on a plant, the attached leave produces VOCs. These chemicals cause the attacked plant as well as the surrounding plants to increase the production of natural pesticides to help defend against the bug.

Protection From Abiotic Stresses

Abiotic stresses like drought or extreme temperatures cause the release of VOCs that improves plant resistance to stress.

Control of Pathogens

VOCs produced by leaves inhibit the germination and growth of of fungi. One of these chemicals, trans-2-hexenal, has been tested as a biofumigant for postharvest fruits like peaches and apricots.

Cultivation of Bacteria on Leaves

There can be up to 10 million bacteria per square centimeter (0.2 sq inch) of leaf surface. VOCs with antimicrobial properties are produced by the plant to encourage certain resistant species to live here and they repel pathogens. The bacteria themselves also produce VOCs. The surface of the leaf is a smelly place!

Roots Produce VOCs to Condition the Rhizosphere

The rhizosphere is a thin layer around plant roots where they cultivate microbes and select species that are beneficial to them. Mycorrhizal fungi can even affect the VOCs plant roots produce.

Do Plants Absorb VOCs?

I mentioned above that plants can’t clean the air in your home, but they are able to absorb VOCs. That may seem like a contradiction, but it’s not.

If you place a plant in a small closed chamber and inject a chemical, the concentration of that chemical does go down because both the plant and soil microbes are able to absorb it. This ability of plants has been demonstrated in several different studies and seems to apply to most plants although each species has a different affinity for a given VOC.

However, our homes are not small closed chambers, and VOCs are not injected once. Our homes are large relative to a plant. The building material (flooring, paint, furniture, carpet etc) is constantly injecting VOCs into the air of our homes. Plants do absorb these compounds but the house is producing them far faster than the plants ability to absorb them. The net effect is that the presence of a plant does not affect the air quality in our homes. This is analyzed in much more detail here.

Plants, Pots and Microbes

The above mentioned study from 2009 produced some other interesting results. They not only tested plants but they also tested the soil and pots for a wide range of VOCs. They also looked for specific VOCs known to emanate from synthetic pesticides.

The microbes in soil are able to both absorb VOCs and produce them. That is no surprise since most living organisms, including yourself produce VOCs. You can easily smell human VOCs in the washroom and in cloths after a good workout.

The plastic pots holding the plants also produces VOCs as do most plastic material.

The plants used in this experiment were commercially obtained and the pesticides used to produce them were still detectable. The plant decomposes these pesticides into other compounds and some of these are classed as VOCs.

How much VOC is produced by each of these sources? I used the data in the study and calculated the total amount of VOC produced by each source, using day time values. This table compares the four plants.

Ignore the VOCs produced by the peace lily for a moment. The plastic pot produced the largest amount of VOCs. The amount produced by plants was about half as much, and the amount from microbes was even less. The least contribution came from pesticides. In the mind of most gardeners the real concern is over the pesticides, but the plastic pots are much worse, if we only consider the total quantity of VOCs produced.

The Power of Flowers

What about that big VOC number for the peace lily? Ninety percent is from one compound called farnesene, which is the fragrance given off by green apples, gardenias and flowering peace lilies. The peace lily in this study was in flower.

Gardeners have no concern about getting close to sniff some farnesene but they are very concerned about synthetic pesticides. The flowering peace lily is producing 427 times as much VOC as the pesticides.

To understand the health concerns you do have to look at the actual compounds being produced not just the total amounts produced, but the numbers do put some sobering perspective on the whole discussion about VOCs.

Do Potted Plants Cause Air Pollution in Your Home?

Sure they do. You might enjoy the fragrance of a peace lily but others may not. Some of the VOCs produced by plants are bioactive and in large enough amounts could cause you harm. It is important to put this into perspective. The main VOCs released by plants are terpenoids, which are the compounds that give plants and flowers their scent, provide signally mechanisms between plants and help attract pollinator. These are all natural compounds.

How serious is this problem. This quote from one of the studies sums it up nicely, “the positive or negative impact of these compounds on humans balanced with the ability of plants to remove other volatile organic compounds is unknown”. We just do not know enough to understand any potential risk.

If you look at the list of VOCs produced by plants you don’t see any of the known harmful VPCs such as benzene and toluene. Just because the names are hard to pronounce like farnesene and trans-2-hexenal does not mean they are are cause for concern.

We do know that bringing plants into the home exposes us to the wide range of chemicals they produce. The concentration of these chemicals will increase in the home compared to the outside world but the amounts of these are still very tiny and are unlikely to cause a problem.

I would be much more concerned about VOCs from your laminated floors, carpets, paint, air fresheners, perfumes and even your artificial smelling deodorant. 🙂