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Respirable crystalline silica dust generated duringstone crushing operations has been linked to chroniclung disease and increased risk of tuberculosis. InIndia, most stone crushing mills operate without anydust control or containment systems. This investigationin the Khurda District of Orissa demonstrated a reduc-tion in respirable particulate mass following the appli-cation of a fine mist of water. Average respirable quartzand cristobalite levels declined 82% and 69%, respec-tively, after water spray controls were installed. Thisfinding suggests that relatively inexpensive modifica-tions that are available in the local market can be effec-tive at reducing silica exposures. Although averageexposure levels, particularly during the dry season, mayexceed the Permissible Exposure Limit for silica, theoverall reductions observed were substantial. Wide-spread adoption of this simple control technology bystone crushers in India could have a positive publichealth impact. Key words: crystalline silica, silicosis,tuberculosis, lung cancer, stone crushers, water spraycontrol, India, airborne dust.INT J OCCUP ENVIRON HEALTH 2008;14:94–103The stone crushing industry in India has beengrowing rapidly due to increasing demand fromthe construction industry and the presentemphasis on developing the country’s infrastructure(e.g., road building). Though reliable statistics are lack-ing for this industrial sector due to its informal nature,it is estimated that there are more than 12,000 stonecrushing units in India, providing direct employmentto 500,000. 1 Most of these operations are labor inten-sive, many involve child labor, and many are located intight geographic clusters close to highways and resi-dential dwellings. This industry has long been associ-ated with exposure to respirable crystalline silica dust.Thousands of workers and those residing in close prox-imity to these operations are exposed to extremely highsilica levels during stone crushing operations. BACKGROUNDHealth EffectsOccupational exposure to respirable crystalline silicacauses silicosis, is associated with lung cancer andtuberculosis, and may be related to the development ofchronic renal disease and autoimmune diseases such asrheumatoid arthritis. The primary factors determiningthe pathogenicity of crystalline silica, in addition to itsstructure, are particle size and concentration.Although respirable crystalline silica particulates aretypically < 10 µm in diameter, studies with human sub-jects have shown the most fibrogenic particle size to beabout 1 µm in diameter (range 0.5–3 µm). 2Silicosis, the most prominent of the silica-related dis-eases, is an interstitial lung disease caused primarily bythe inhalation of free crystalline silica. Chronic silicosishas a latency period of 10-30 years of exposure to res-pirable crystalline silica dust at relatively low concen-trations. 3 Acute silicosis, however, usually develops afterexposures to very high levels of respirable crystallinesilica resulting in onset of symptoms in as little as a fewweeks to five years post exposure. 4 Studies have alsoshown a three-fold increased risk for developing tuber-culosis (TB) in workers with silicosis compared to thosewithout silicosis. 5Although there have been many epidemiologiccancer mortality and morbidity studies in silica-exposed workers, the issue of carcinogenicity was notresolved until the late 1990s. The International Agencyfor Research on Cancer (IARC) has classified inhaledcrystalline silica in the form of quartz or cristobalitefrom occupational sources as carcinogenic to humans(Group 1). 6 Among a cohort of 3,246 U.S. workers in94Reduction of Respirable Silica Following theIntroduction of Water Spray Applicationsin Indian Stone Crusher MillsPERRY GOTTESFELD, MPH, MARK NICAS, PHD, MPH, CIH, JOHN W. KEPHART, MSPH,KALPANA BALAKRISHNAN, PHD, RICHARD RINEHART, SCD, CIHReceived from Occupational Knowledge International, San Fran-cisco, CA (PG, JWK), University of California at Berkeley, School ofPublic Health, Berkeley, CA (MN), Sri Ramachandra Medical Col-lege and Research Institute, Chennai, India (KB), and the NationalInstitute for Occupational Safety and Health, Washington, D.C.(RR). This research was funded by the U.S. Agency for InternationalDevelopment, ERM Group Foundation, and by donations to Occu-pational Knowledge International. Significant equipment and in-kind support was provided by the National Institute for OccupationalSafety and Health, Clayton Group Services, Inc., Health ScienceAssociates, Millipore Corporation, Sensidyne, and SKC Inc. Addresscorrespondence and reprint requests to: Perry Gottesfeld, MPH,Occupational Knowledge International, 220 Montgomery Street,Suite 1027, San Francisco, CA 94104, U.S.A.; telephone: (415) 362-9898; fax: (415) 362-9410; e-mail: <pgottesfeld@okinternational.org>Disclosures: The authors report no conflicts of interest.