Environmental Health: Plants

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Plants have played a pivotal role in the evolution and maintenance of the planet: regulating the physical environment and providing for the needs of animals, including humankind. We have a symbiotic relationship with plants, and the sooner we reintegrate ourselves with the plant world and work with it, rather than against it, the sooner we will start getting our priorities right. We can begin this process by understanding the many roles that plants have played and continue to play in the evolution of the ecosystem. They embody a natural technology and architecture. The architecture is there for all to see; the sophistication of their technology we are only just beginning to appreciate.

Plants convert carbon dioxide and water into oxygen and organic matter, using solar energy through the process of photosynthesis. Animals and microorganisms consume most of the oxygen made by the plants, returning carbon dioxide to the air. All the oxygen in the biosphere is produced by plant life, either in the sea or on land. Of course, other nutrients are absorbed from the soil and air by plants; and , as well as producing cellulose as their basic construction material, plants synthesize prodigious numbers of chemical compounds.

Plants can actually provide us with many solutions to problems raised in this guide, and in this Health section in particular. As well as providing for our basic needs of food and shelter, they can help us solve many of the problems of pollution that are so urgently in need of ecological remedies. In return, we need to learn to look after plants and nurture them: a process that will, in itself, put us back in touch with the natural processes necessary for a sustain able world. However, it should be said that houseplants are not universally popular: some people dislike the increased humidity that plants engender.


In the wider world we can see how plants are used to meet our food, energy, and , to some extent, medical needs, but how can they be used in the home? We shall start with the role that plants can play in pollution control.

Plants as Pollution Controllers

A NASA scientist has conducted experiments to see what use could be made of plants in the confines of a spacecraft. He found that plants were particularly good at cleaning chemical pollutants out of the air. Different plants absorbed different chemicals. Not only that: plants also absorb pollutants from water through their roots, and microorganisms in the soil absorb pollutants. The most famous example of a plant’s ability to absorb a pollutant in this way is the common spider plant, which removes formaldehyde from the air. Formaldehyde is a very common indoor domestic pollutant, originating in chipboard and other manufactured boards and plastics. As an air pollutant, it has been implicated in “sick building syndrome” and other environmental conditions. The spider plant will grow almost anywhere, and it reproduces more easily than almost any other plant. It is difficult to overwater and thus is a favorite indoor houseplant. Keep half a dozen large healthy plants in your kitchen (particularly if it is newly installed), and at least the effects of one indoor chemical will be diminished.

This is just one example. Very little research has yet been carried out to discover which plants absorb which pollutants, and how they can do this most effectively. We may find that, in the future, factories will only be permitted to generate pollution if it can be absorbed by adjacent plantations that can synthesize these toxic by-products. Solar aquatics, which uses a greenhouse environment to speed up the absorption process in temperate climates, is beginning to provide viable alternatives to much more expensive sewage treatment plants. Countries that have plenty of sun and water have a ready advantage in this emerging technology: there is a particularly successful scheme outside Calcutta where plants clean the water and fish (which are harvested for human food) feed on the plants.

To return to our homes, here is a brief list of plants that can help clean the air in different ways:

• Dwarf banana (Musa cavendishii)

• Spider plants (Chiorophytum comosum)

• Golden pothos (Epipremnuni aureum)

• Chinese evergreens (Aglaonema modestum)

• Peace-lily (Spathiphyllum)

• The genus Peperomia

• Snake plant (Sansevieria spp.)

• Goosefoot plant (Nephthytis syngonium)

• Ivy arum (Scindapus aureus)

There must be many more plants that could be used to solve different pollution problems. One intriguing part of this research is that it has been found that the ability of a particular plant to absorb and metabolize a chemical increased when it was exposed to the chemical for long periods of time. So perhaps plants can learn to use the particular pollutants that are peculiar to your home! Increasing light levels also increased the rate of absorption. It is essential that more research be done on the number and size of plants which might deal with particular pollutant loads. It is definitely worth watching out for more detailed information as it becomes available.

Other Ways That Plants Condition the Quality of Our Air

Plants can be used in many ways to improve air quality and provide a more equable indoor climate. They can help conserve negative ions, they can remove certain odors, and they can moderate the humidity through evapo-transpiration, in which oxygen and water are discharged into the room.

Besides the plants’ leaves, the soil in which they grow can also act as an air filter; it may be possible to design special filter/plant beds through which air is drawn. This method of air cleaning has been tested and shows definite promise. It is particularly the products of combustion that are success fully filtered out.

Plants to Clean Water

There are various methods that use plants to clean pollutants from water. In Britain, reed-beds are being experimented with, in an attempt to deal with household wastewater. This is an open-air process that involves a sequence of differently shaped pools or reedbeds through which the water flows. Each pool has a different function, using different plants, microbes, and other organisms to extract different pollutants and nutrients. Solar aquatics (already mentioned earlier in this section), which uses a sequence of glass containers in a greenhouse, is perhaps the most successful of the many experiments originating in the United States. All these experimental methods are new ways of harnessing biological processes to imitate the way nature cleans dirty water, only carried out in a more systematic manner.

Both these methods produce clean water, processed at a reasonable cost and with useful by-products. Although not yet developed in a form which could be used in an inner-city house, if you live in the countrywithout access to a sewer, the system of reedbeds provides a ready alternative for processing your wastewater and sewage.

Plants for Noise Control

Banks of plants can absorb sound very effectively. If you have a particular problem, see whether plants can help solve it. If you experience traffic noise, and have garden space between you and the road, it is possible to grow a dense thicket of trees and bushes to screen out much of the noise. If it is dense enough, this thicket will even help absorb some of the car exhaust gases. Inside the home, if you have a reverberation problem, plants can be placed strategically around the rooms to help to reduce echoes by absorbing sound.

Plants for Fragrance

Plants are traditionally used to give fragrance to a garden. Often, however, the indoor plants that we use have little smell. The following are a list of those houseplants that are particularly fragrant:

• Moonflower (Ipomoea alba)

• Citrus plants (miniature varieties)

• Coffee plant (Coffea arabica)

• Tree-tomato (Cyphomandra betacea)

• Angel’s trumpet (Datura suaveolens)

• Various species of Daphne, (Daphne mezereum is popular)

• Chinese jasmine (Jasminium polyanthum)

• Luculia gratissima

• Eucalyptus citriodora

You will have to grow plenty of plants, and place them in a sunny location, to gain the best results.

One important note of caution: be especially careful in bringing home new houseplants if you have young children at home. Many of these plants have shiny foliage, pretty blossoms, or colorful berries, but can be highly poisonous if ingested.

Plants for Taste and Nutrition

To be able to grow indoor plants that we can actually use is particularly satisfying and helps to increase our motivation. Herbs are an obvious choice. The advantages of fresh herbs over dried ones are important, for some herbs achieve their real flavor only when fresh. Most herbs can be grown inside; however they generally need plenty of sunshine, so potted herbs need to be placed on a sunny windowsill or in the conservatory. Parsley, chives, sweet basil, pot marigold (Calendula), and nasturtiums all do well in pots.

Above all, indoor plants can give us aesthetic pleasure. They allow us to bring some of the freshness and beauty of a garden inside the house. By integrating plants into your home and adapting it to their needs, you will find that they will in turn provide for even more of yours.

The External Use of Plants

Elsewhere in this guide, in the EXTERNAL SPACE section, plants have been suggested for many different functions:

As external climate regulators providing shade, windbreaks, insulation, rain protection, and UV protection

• As habitats for wildlife and beneficial, pest-controlling insects

• As barriers for security and privacy

• As coverings for facades and roofs

There remains perhaps the most important aspect of all: how we can look after plants, particularly indoors, so that they can fulfill these functions successfully.


Plants have certain needs that are very simple. They require water, nutrients, air, light, and warmth; and , perhaps most important of all, they need our care.

Plants will differ greatly in their individual growing requirements; fortunately, there are many plant books and web sites exactly what you have to do to provide for and maintain plants in good health. One of the main considerations is the humidity levels that they require. Many houseplants like a humidity of around 60%. Most homes are much dryer than this: many living rooms have a humidity of about 20%. Bathrooms and kitchens tend to have a much higher humidity, around 50%, and many people choose to keep their plants in these rooms most of the time. Overwatering is a common mistake with houseplants; it is therefore important that just one person oversees the watering and knows the requirements of any particular plant. The right level of light is also important: different plants have very different requirements. A few plants can survive dark interiors, but most require periodic placement in a sunny spot if they are to remain healthy. Choose appropriate species for different growing environments in the house, and be aware of the size your plants will grow to. If you get into good habits and are always willing to learn, you are likely to gain much enjoyment and satisfaction from growing and tending plants.


+ Learn about how to look after plants from houseplant books and web sites; learn about the particular needs of the plants that you have.

Choose appropriate places in your home for houseplants and work on setting up the right environment.

+ Work out where your most polluting sources are likely to be and place plants close to them.

+ Set up a corner, worktop, or cupboard where you can keep all your plant maintenance equipment and books.

+ Set up a little greenhouse, bay window, dormer, or roof-light so that you can place plants there to recuperate and also grow new ones from seeds and cuttings.

+ Consider ways of watering your plants with gray water.

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