What is organic-dust toxic syndrome?

Two weeks ago, for five days, the National Centre for Farmer Health, which is based in Hamilton and affiliated with Deakin University, ran a five day Agricultural Health and Medicine course.

I spoke on the first day of the course about respiratory disease affecting farmers. There were two aspects of the talk I considered to be blog-worthy.

The first is ‘Organic dust toxic syndrome’ (ODTS). This is an entity about which I was entirely naïve until I began to practice in the Western District and read about occupational hazard facing farmers.

Organic dusts are those inhalable particles that arise from grains, and also from animal dung when it is dried and crushed – for example, under foot in a stock yard on a dry day. They contain multiple potentially hazardous compounds, but perhaps the most significant (and most prevalent) is endotoxin. This fragment of gram negative bacteria is thought to be very significant in inducing immune system inflammatory response, and a key mediator of illness in life-threatening gram negative sepsis.

Farmers, grain workers, swine handlers (enclosed livestock environments are particularly hazardous) may inhale this substance. If they do, then it can act in the airways to induce an acute inflammatory response. The resultant illness – ODTS – is ‘flu like’ and, I am sure, often misdiagnosed as such. The key is that there will usually be a history of massive exposure to inhaled organic dusts; for example, a particularly dry and busy day at the stockyards or silo with a lot of dust in the air. If many workers had the same exposure then many of them will likely to be sick at the same time. It resolves, like the flu, over several days but will recur after similar repeated exposure.

A good description of ODTS, along with a comparison of the less common ‘Farmers Lung’, is found on the University of Missouri website. I am concerned that this entity is common, but often misdiagnosed as viral illness or pneumonia, and remains therefore as a hidden, significant occupational hazard for agricultural workers. Those of us who provide care to such workers – particularly GPs – need to be aware of it and ask the appropriate occupational questions.

The second thing I wanted to share was the following graph from the Sustainable Farm Families research.

This research used the Piko6 device as a sort of spirometer (it measures FEV1/FEV6 rather than FEV1 over FVC) to obtain lung function measures from farmers. If the ratio was below 75% then it was reported as 'poor' lung function. Note the discrepancy between dairy farmers and other farmers - with five to seven percent more farmers in cropping, cattle and sheep ventures having ‘low’ lung function when compared with dairy farmers. This needs to be teased out further, but does lend one to suspect that there are less respiratory toxins in dairy farms than in other farming environments in our district.

Andrew