How Foliage Plants Affect Office Workers, School Children, and Health Care Personnel – 3

This is a continuation of the study published by Green Plants for Green Buildings that talks about the effect of plants and artificial day-light on the well-being and health of office workers, school children and health care personnel.

Article Reference: Green Plants for Green Buildings

THE EFFECT OF PLANTS AND ARTIFICIAL DAY-LIGHT ON THE WELL-BEING AND HEALTH OF OFFICE WORKERS, SCHOOL CHILDREN AND HEALTH CARE PERSONNEL

Tove Fjeld, Dr. sci. Fjeld Consulting AS, Nordbyvn 38 1406 Ski, Norway and Charite Bonnevie, Specialist in Occupational Medicine, Nordea Bank, Oslo, Norway

Study 4. Evaluation of the use of foliage plants and artificial day-light among office workers on health and discomfort complaints, well-being and sickness absence.

Building on the background of the previous studies, there was a need for trying to separate effects of plants from effects from artificial daylight. A small investigation was established among workers in Nordea Bank, Oslo, during the period November 2001 –March 2002. All together, 48 office workers participated. Information regarding health and well-being was sampled from the participants twice before intervening the work environment, and three times after intervention. The work environment was intervened as follows: 16 people had plants on their office tables close to their personal computer, 10 people were given a new light environment by changing the light sources to a more day-light-like spectrum, 10 people received both plants on their work tables, as well as a new light environment, while 12 people served as a control group.

The level of complaints was significantly lower among workers that had plants on their office tables. Lowest level of complaints was found if plants were supplied in combination with a change in light environment. A smaller reduction in complaints was found if only the light environment was changed to artificial daylight.

Semantic evaluation of the work environment by the participants concluded that a change in light environment alone, did not affect the satisfaction level of the visual environment. By introducing plants on the work tables or establishing a combination of plants and a change in light levels, a significantly more positive evaluation of the work environment was reported: The score level was found to be 2.9 among the control group and the group of participants that got a change in light environment, as opposed to 2.4 if plants were introduced, and 2.2 if a combination of plants and new light environment was established (scores: 1 = very satisfactory, 3 = medium satisfaction level, 5 = very unsatisfactory) (Fjeld and Bonnevie 2002).

DISCUSSION

There may be several explanations for the results obtained:

1. Effect on air quality:

During the 1980's reports were published indicating that indoor plants may have the ability to reduce the level of chemical compounds in the air. Leaves, stems and roots work together with micro-organisms that live in the root zone, creating an ecosystem that can function as an air filtering system.

Bill Wolverton and his research group showed in laboratory studies that plants used as ordinary houseplants may reduce the level of different chemical compounds in the air. If the plants were exposed to high concentrations of chemicals in sealed growth chambers, the concentration was reduced by the plants. Chemicals tested were f. ex. formaldehyde, benzene, trichloroethylene, carbon mono-oxide and NOx. Approximately 20 different plant species were included (Wolverton et al. 1989).

More recent studies from Germany and Australia have confirmed the ability of plants and the ecosystem of plants and micro-organisms to be possible powerful air purifiers, even if the concentration of chemicals is low (Schmitz 1995, Wood et al. 1999). This air-purifying ecosystem will need a period of time (approximately 14 days) to adapt to the chemicals that occur in the air. The system seems to be independent of light – which means that the photosynthetic activity of the plants is less important than the symbiotic activity of roots and microorganisms – at least after the system has become adapted to the environment.

The human body is also able to detect changes in the indoor air quality far below the guideline concentrations, as shown by Forsberg and his team (1997) of occupational medicine experts. This means that even small changes in chemical impurities of the air, may influence health and discomfort symptoms.

Tests carried out both in the US and in the UK, have shown that plants may also increase the indoor air humidity. It has been shown that if the air is not ventilated, the increase in humidity may be from 0 to almost 15%. In a ventilated room, the increase may be 3-5 % (Lohr 1992a). Plant species with a high transpiration rate, increases humidity most. The numbers of plants will of course have a large impact. The humidifying effect of the plants might be important, since many indoor environments suffer from low air humidity.

Plants in a room may reduce the dust level of the air, as found by Lohr and Pearson-Mims (1996). The dust content of the indoor air is often too high, and might irritate mucous membranes in eyes and respiratory organs (throat, nose). An increase in air humidity may bind more of the dust, and thereby reduce the health complaints. The large leaf surface of plants probably promotes sedimentation of dust from the air, thereby reducing the dust level. We would expect that plants placed close to the computer – where both dust level and the level of static electricity is often high, might reduce irritations in respiratory organs caused by charged particles. The supposed changed micro-climate around the plant material is more likely to affect people’s perception of the physical air quality if the plants are placed close to the persons, and at a place where people will be exposed for this micro-climate for some time during their working days. This corresponds with results found by van Dortmont and Bergs (2001), who concluded that work efficiency and well-being were significantly higher among workers that spent more than 4 hours at their computer desk if their desks were supplied with plants.