Phoenix Journal · LEV & Air Quality
Flour looks harmless, but the fine dust it throws off is one of the most common causes of occupational asthma in Britain. Bakers develop asthma at among the highest rates of any trade, and the cause is breathed in long before anyone notices.
Flour is one of those materials that feels completely benign, which is exactly why the risk it carries is so often missed. The fine dust released when flour is tipped, sieved, weighed or dusted onto a bench is a respiratory sensitiser, and breathing it in regularly can cause baker's asthma, a form of occupational asthma. Under COSHH it is a hazardous substance, no different in principle from the solvents and dusts of heavier industry. Flour and the enzyme improvers used with it can also cause dermatitis, so the hands are at risk as well as the lungs.
The scale of the problem is easy to underestimate. Bakers sit among the very highest of any occupation for new cases of occupational asthma, and the trend towards more seeded and enzyme-improved products has added to the mix, because the amylase enzymes used as improvers and the proteins in seeds such as sesame are potent sensitisers in their own right. Rye, soya and buckwheat flours can sensitise too, so it is not only wheat that carries the risk.
What makes a sensitiser dangerous is the one-way nature of it. Once a worker's airways have become hypersensitive, even very low levels of flour dust can trigger an attack, and the change does not reverse. That is why the goal is never simply to keep dust at an acceptable level but to keep as many workers as possible from ever becoming sensitised in the first place. Some people are more susceptible than others, but the dose-dependent nature of the risk means nobody is immune once the dust is high enough.
A limit, and a lower target
Flour dust carries a workplace exposure limit of 10 mg/m3 averaged over eight hours, with a short-term limit of 30 mg/m3 over 15 minutes. But because flour is an asthmagen, the HSE is clear that exposure should be reduced as far below that limit as is reasonably practicable, not simply held beneath it. Crucially, the HSE also states that good control practice usually achieves less than 2 mg/m3 over eight hours, so the practicable target is a small fraction of the legal ceiling.
That gap between the limit and what good practice achieves is the whole game. Studies of bakeries consistently find the highest exposures at the dough-making and flour-handling stations, where tipping and mixing throw the most dust, while packing and finishing areas read far lower. Knowing which tasks are the peaks tells you where to spend the control effort, because an average across the day can hide a punishing few minutes at the mixer. Research bears this out, with a raised risk of rhinitis reported above roughly 1 mg/m3 and of asthma above about 3 mg/m3, well within reach of an uncontrolled mixing station.
You cannot judge any of this by eye. The finest, most inhalable dust is invisible in normal light, so a bench that looks clean can still be putting sensitising dust into the air. A dust lamp, a bright beam shone across the work, is the simplest way to reveal where dust is actually being generated and whether the controls are catching it.
Technique and extraction
Control follows the usual order: first stop dust being made, then capture what remains, then protect the person. Simple engineering pays off here: fitting a sleeve to the end of a flour delivery pipe and a lid to the mixer tub have both been shown to cut measured exposure sharply. Low-dust flours, gentle handling instead of throwing, scraping rather than brushing, and lidded or sleeved mixers all cut generation at source, while local exhaust ventilation at tipping, sieving and weighing points captures what is left. Respiratory protection is the backstop for the dustiest tasks, and for fine flour that usually means a mask to a high standard, which only works if it seals to the wearer, so face fit testing, why it is not optional is as relevant in a bakery as it is on any building site.
Catching it early
Because baker's asthma develops slowly and irreversibly, health surveillance is a normal expectation wherever flour dust is handled: a respiratory questionnaire and lung-function checks that can spot the earliest signs while a worker can still be moved away from exposure and recover. The pattern of a familiar workplace substance quietly turning into a lifelong condition is the same one told in occupational asthma, causes hiding in plain sight, and in baking it is especially cruel, because sensitisation can force a skilled baker out of the trade for good.
Questions
It is a form of occupational asthma caused by breathing in flour dust and related sensitisers such as amylase enzymes. Once a baker becomes sensitised, even low levels of flour dust can trigger attacks, and the condition does not reverse.
The workplace exposure limit is 10 mg/m3 over eight hours and 30 mg/m3 over 15 minutes. Because flour is an asthmagen, exposure must be reduced as far below that as reasonably practicable; the HSE says under 2 mg/m3 is usually achievable.
Work in the right order: reduce dust at source with low-dust flours and gentle handling, capture the rest with LEV at tipping, sieving and weighing, then use well-fitted respiratory protection for the dustiest jobs. Avoid dry brushing and never throw flour.
Phoenix Duct Clean · by the numbers
Flour dust needs LEV at the tipping, sieving and weighing points, tested to prove it captures rather than just moves air. Phoenix examines and tests LEV to COSHH Regulation 9. UK-wide.