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RECYCLING organic household waste could be bad for your health. Garbage bins
containing separated organic leftovers such as banana skins, potato peelings and
apple cores release far higher numbers of potentially harmful bacteria and
moulds into the kitchen than those containing mixed garbage, Dutch researchers
have found.

Dick Heederik and his colleagues in the environmental and occupational health
group at Wageningen University in the Netherlands say that the contaminants
include bacteria and moulds known to aggravate common respiratory ailments, such
as asthma. Millions of environmentally minded Europeans could be at risk when
they dutifully segregate organic materials from their household waste for
collection and recycling as compost.

Heederik鈥檚 team made the discovery after collecting and analysing household
dust from 99 Dutch households, some with segregated and some with mixed waste.
They decided to carry out the study after complaints from people when
segregation was introduced in the Netherlands six years ago. 鈥淭here were loads
of complaints about the smell from organic bins, and some people with
respiratory illnesses said their symptoms got worse,鈥� says Heederik. The reason,
he says, is that the humid state of pure organic waste suits microorganisms
better than mixed waste, which 鈥渄ilutes鈥� the organic material.

The team tested for cell fragments called endotoxins, which are released when
bacteria die. Their levels reflect concentrations of bacteria in the dust. 鈥淚f
exposure to these is high enough, the endotoxins themselves cause coughing,
breathlessness and some flu-like symptoms,鈥� says Heederik.

To detect moulds, he and his colleagues screened dust for
beta-glucans鈥攕ugars found in the coatings of numerous fungi. Beta-glucans
have been shown to cause lung and throat inflammation. The team also screened
for exopolysaccharides, polymers found in the cell wall of common
Aspergillus and Penicillium moulds.

In homes where organic bins regularly remained unemptied for a week or more,
levels of the bacterial endotoxins were three times as high as in homes with
unseparated waste. Levels of the mould materials, exopolysaccharides and
glucans, were even higher, some up to eight and five times as high respectively
compared with households that mix their waste.

In houses with dust-accumulating textile floors, as well as an organic waste
bin, concentrations of the microbial agents were higher still鈥攁nything
from 25 to 840 times as high as in houses with neither risk factor.

鈥淭he solution is to keep the organic waste bin outside, but in many cases
that鈥檚 not possible in downtown areas, where there鈥檚 less space,鈥� says Heedrick.
The other remedy is to empty the bin more regularly into the larger, roadside
receptacles provided by the authorities.