Gardening with wood chip mulch can cause inflammation of the lungs -- and in some people, a brief bout with flu-like symptoms, including fever and achy muscles, according to a UCSF study.

The report is the first to verify such a lung reaction and illness after exposure to low-level organic dust from wood mulch -- levels similar to those that might occur when gardening around the house.

Shoveling wood chips can cause organic dust toxic syndrome (ODTS), an illness that also can occur after inhaling cotton, grain, hay, and other dusts or aerosols, says Paul Blanc, MD, chief of occupational and environmental medicine.

Weekend gardners who use wood mulch may want to wet down the chips to reduce the dust or wear a mask to prevent breathing too much of it, Blanc advises.

He says many dismiss ODTS as a “24-hour bug” and do not connect the illness to breathing the dust. Usually, the person feels achy four to six hours after exposure, has chills, develops a fever, goes to bed thinking she or he has the flu, and wakes up in the morning feeling better.

Because job-related wood chip mulch exposures usually are at higher levels than that typically associated with home gardening, Blanc and his colleagues wanted to find out if signs of ODTS would occur after a brief, low-level exposure.

In a study, published in the April issue of the Journal of Occupational and Environmental Medicine, they tested six adult volunteers who shoveled wood chip mulch piles in a local city park for two hours. Three ended up with the classic flu-like symptoms of ODTS.

The researchers also tested the mulch for levels of endotoxins-- organic molecules often found in damp, decomposed mulch -- and they carried out an extensive study of the potential inflammatory cells the volunteers had in their lungs after the exposure.

They found that after wood chip activity, there was an increase in the number of inflammatory cells -- a reaction of the body's immune system to the exposure, Blanc says.

They also detected increased levels of biochemical messengers -- cytokines -- that stimulate the release of inflammatory cells and trigger the fever and flu-like signs. This finding supports others showing that these biochemical messengers are what mediate the symptoms.

"The amateur gardener is not likely to have a major problem over time, but if you did very heavy gardening work with wood mulch and that night had flu-like symptoms, it may very well be explained by this biochemical mechanism," he says.

1st appeared 5/27/97