Occupational asthma inafactory with acontaminated humidifier

Thirty five printers whohadworkrelated wheeze, chest tightness, or breathlessness kept twohourly records oftheir peakexpiratory flowforatleast twoweeks. Theyallworkedina factory supplied byairfromcontaminated humidifiers. Thepeakflowrecords showedconsistent workrelated deterioration in15workers, nineofwhomhada diurnal variation inpeakflow exceeding 20%.Tenworkers keptfurther records after thehumidifiers hadbeencleaned, other workpractices remaining unchanged. There was substantial improvement inall10workers, implying thatmaterial fromthecontaminated humidifier was thecause oftheworkrelated changes inpeakflow. Thepatterns ofworkrelated changes inpeakflow fell into four groups:falls maximal on thefirst workday,falls maximal midweek, falls equivalent eachworkday,andfalls progressive throughout theworking week. Three quarters ofthis last group hadimmediate prick test responsestohumidifier antigen, which were negative inalltheothers withworkrelated changes inpeakflow. Thissuggests that theprogressive daily deterioration pattern alone isdueto anIgEmediated responsetohumidifier antigens. A large rangeofmicroorganisms was identified inthehumidifiers. No single microorganism appeared tobetheantigen responsible forthe precipitating antibody seenin75%ofthestudy population. Industrial humidifiers arenow a wellrecognised source ofrespiratory problems, suchashumidifier fever andallergic alveolitis; butsofarthere have beennoreports ofanyassociation withoccupational asthma. Although thecauseofthesediseases isasyetunknowntheexcessive growth ofmicro- organisms within thehumidification system seemsto beacommonfactor toalloutbreaks, andthere is everypossibility thattheseorganisms or their metabolites arecapable ofacting onmorethanone element oftheimmunesystem. Thecontrol ofhumidity isofprimary importance incertain industries, especially inprinting, where thesize ofpapersheets varies withchanges intheir watercontent; anditisalso necessary forcomfort to maintain aminimumof40%relative humidity level