But new research has confirmed that certain groups of specialist contractors are at particular risk, with tasks such as final-house cleaning generating the highest levels of dust, according to Farmers Weekly Interactive.

Workers on poultry farms are exposed to an airborne cocktail of particles, including feathers from the birds and dust from dry bedding and droppings. In addition, there are mites, bacteria, fungal spores, endotoxins (toxic chemicals released from dead bacteria) and even pesticide and fertiliser residues.

Larger dust particles are stopped in the nose and upper breathing passages where they can cause irritation, bronchitis and sometimes asthma. However, smaller ones, such as spores from mouldy straw that cause Farmer’s Lung, penetrate into the deeper recesses of the lung.

Symptoms include irritation of the nose and eyes, fever and general aches and pains, headache, chest tightness, coughing, wheezing, breathlessness and weight loss. Workers may become allergic or sensitised to specific agents and suffer extreme reactions if then exposed to even low levels for short periods. Severe asthmatic attacks can be fatal.

In general, the higher and the more frequent the exposure, the greater the risk of developing breathing difficulties. However, there is some evidence that short-term, peak exposures may have a significant bearing on sensitisation.

The Health and Safety Executive (HSE), recently commissioned the Health and Safety Laboratory (HSL) to conduct a survey of both the egg and broiler sectors, which included personal monitoring of workers carrying out typical farm tasks.

The HSE has worked closely with the industry to produce guidance focusing on the range of tasks that have place workers at greatest risk and provides practical advice on how to protect workers’ health.

The new guidance, endorsed by both the British Poultry Council and the British Egg Industry Council, highlights good working practice based on creating less airborne dust and phasing-in vehicles with enclosed, ventilated cabs with filtered air intakes as older machines are replaced.

However, the guidance also recognises the important part that respiratory protective equipment will continue to play in the foreseeable future and provides additional advice on its effective management.