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Multi-tasking plants in combating air pollution

Air pollution is on the rise. When indoor and outdoor air pollution are combined, WHO estimates that in 2012, some 14% of deaths were due to chronic obstructive pulmonary disease (COPD), or acute lower respiratory infections, and 14% of deaths were due to lung cancer.

Emissions from vehicles are a major contributor to air pollution. They release nitrogen dioxides and fine particles, leading to local pollution especially in urban areas. The most damaging type of outdoor air pollution is fine particulate matter smaller than 2.5 micrometres in diameter (PM2.5 ).
Other sources contributing to PM2.5 concentrations can come from afar however, as there have been many occasions where ‘Saharan dust’ has triggered respiratory problems in the UK population, but the dust has been found to contain these fine particulates and ammonium nitrate from Europe.

Air pollution reduces overall life expectancy in healthy individuals, but in combination with other existing health conditions can also cause early death.

A study from 2017 looked at the role of woodland, grassland, moorland and crops in removing a suite of air pollutants which are known to have substantial impacts on human health. The study looked at levels of PM2.5, nitrogen dioxide, ground level ozone, and sulphur dioxide in these areas. 

The study showed that plants are great at removing pollutants right across the UK and this overall reduction in the levels of pollutants leads to a substantial health benefit.

Several groups got together and estimated the health benefits of removing each pollutant and calculated the economic value. The main health impacts originate from respiratory and cardiovascular health effects, and deaths. The benefits are greater in urban areas because that is where most people live.

Plants remove air pollution by providing a large surface area for particulate matter to settle on, and by active uptake of gases into the leaves or chemical reactions with the leaf surface. Collectively these processes are called ‘dry deposition’. The amount of pollution a plant can remove depends partly on its leaf area and size, but also varies greatly depending on the weather, the time of year (for deciduous species which drop their leaves in winter), and on the other pollutants present in the atmosphere.

The health benefits calculated were substantial, with estimated avoided health costs of one billion pounds in 2015, the majority of this is from removal of PM2.5. The study also estimated 5,800 fewer respiratory hospital admissions, 1,300 fewer cardiovascular hospital admissions, 27,000 less life years that were lost, and 1,900 fewer premature deaths.

So it looks like if we are filling our garden or hedges with plants, we want those with big surfaces that don’t drop leaves Autumn-Winter.

Meanwhile, indoor air pollution is also a constant problem and a threat to health. So looking further into the idea of how houseplants can fend off the potentially harmful effects of volatile organic compounds (VOCs), a main category of air pollutants, a team of researchers have made some new discoveries. They found that certain plants are better at removing specific compounds from the air – this is especially meaningful for indoor air, as studies have shown that interior air can have three to five times more pollutants than outside (apart from in high traffic areas).

VOCs include things like acetone, benzene, formaldehyde and tolulene – they are emitted as gases and can cause short- and long-term health effects. People with asthma and COPD are especially sensitive. They are invisible to the eye and come from common things many of us have around the house, things as innocent-seeming as candles, furniture, copiers and printers, cleaning chemicals.

Since the NASA research in the 1980s, a number of studies have looked into how plants improve air quality, but most of the research has looked at the removal of single VOCs by individual plants from the air; but one groups wanted to compare the efficiency of simultaneous removal of several VOCs by a number plants. The team used a sealed chamber in which they monitored the VOC concentrations over several hours with and without a different type of plant. For each plant they measured the VOCs the plants took up, how quickly they removed these VOCs from the air, and how much of the VOCs were removed altogether. They gathered five plants (spider plant, dracaena, Caribbean tree cactus, bromeliad and jade plants) and gave them 8 VOCs.

They found that all of the plants were good at removing acetone, but the dracaena plant took up the most, around 94 percent of the chemical. The bromeliad plant was great at removing six of the eight VOCs, taking up more than 80 percent of each over a 12-hour sampling period. Likewise, the jade plant was very good for toluene.

Particular botanicals and nutrients from food have been tested in combatting all sorts of nasty bits floating around in our air, so take a look at our products!

Photo by Thomas Somme on Unsplash