G.L. Mitchell

Self-reported Noise Exposures Among Ohio Cash Grain Farmers

As part of the NIOSH-funded Ohio Farm Family Health and Hazard Survey n(OFFHHS), self-reported noise exposure data were collected from more than 1,700 nPrincipal Operators (POs) of cash grain farms. Information on exposure to noccupational and non-occupational noise sources was obtained by means of a statewide nmixed-mode survey.With respect to occupational sources, nearly all survey respondents nreported a history of cabless tractor operation, approximately 80% had operated a chain nsaw, and approximately 70% had operated a combine. About 1/3 respondents reported ncurrent employment in a noisy job in addition to farming, while nearly 20% reported a nhistory of non-agricultural noisy employment. The most frequently reported nonoccupational nsources of noise exposure were hunting (51.5% of respondents), nmotorcycle riding (21.2%), and target shooting (20.5%). Self-reported equipmentspecific ndata on total years of operation or use, days of operation or use per year, and nmean hours of operation or use per day were used to estimate lifetime hours of nexposure to noisy activities/tasks. Of the more than 61 million cumulative lifetime nhours of exposure reported by the 1,700+ respondents, more than half was accounted nfor by operation of cabless tractors. In addition, 2/3 respondents reported they never nwear hearing protection when they operate or are around noisy farm equipment. nAttempts to identify factors associated with use of hearing protection revealed that nalthough the prevalence of usage varied by age and education, use was poor across all nsubgroups examined, suggesting that agricultural workers of all ages and levels of neducation would benefit from interventions designed to reduce the incidence of noiseinduced nhearing loss.

Tear exchange and oxygen reservoir effects in silicone hydrogel systems.

Purpose. The effects of oxygen reservoir and tear exchange are known for conventional hydrogel contact lenses. This study attempted to (1) confirm their presence in lenses of a silicone hydrogel (SH) material and (2) evaluate their individual and combined contributions to hypoxic relief of the cornea. Methods. Corneal oxygen uptake rates were measured polarographically for 10 OD corneas immediately after 300-sec periods (equivalent to 60+ blink cycles) of: (1) nonblink wear of a 0 Dk/L polymethylmethacrylate (PMMA) cap lens; (2) nonblink wear of that cap lens with a SH lens inserted between it and the cornea; (3) regular blinked wear of that same lens combination; (4) nonblinked wear of the SH lens alone; and (5) normal open-eye, non-lens wear. The rates for each eye had a ratio with its own baseline (no lens) rate, and the total sample mean was calculated for each condition from those individual eye means. Results. (1) Under nonblink conditions, a 28% reduction in corneal oxygen demand was observed when a SH lens was inserted under the PMMA cap lens versus without. (2) When regular blinking was added to that lens combination, corneal oxygen demand decreased another 8%, for a total of 36%. The combination of SH insertion and blinking did achieve a statistically significant difference (P <0.05 by the Dunnett test) from the nonblink, 0 Dk/L, maximum deprivation condition. Conclusion. The statistically significant hypoxia reduction observed with the SH lens insertion and blinking indicates the additive presence of two factors: (1) a lens reservoir effect caused by the SH lens and (2) a bulk-flow tear exchange effect caused by blinking. Their respective contributions to the reduction of corneal oxygen demand over the period studied were found to be in the ratio of 3.4:1.

Mixed-mode Survey of Cash Grain Farmers Yields Mixed Response

A multiple-phase, population-based health and hazard survey of Ohio cash grain nfarms and farmers is currently underway. The project was designed as a collaborative neffort between Ohio State University, CDC/NIOSH, and the State of Ohio. In nPhase 1 of the project ( June to November 1993), a stratified random sample of 4,860 ncash grain farms was selected from a comprehensive statewide roster. A mixed-mode nsurvey (i.e., a self-administered, mailed questionnaire, with telephone follow-up of mail nnon-responders) was then conducted to obtain health and hazard data of interest. The ncontent and design of the questionnaire was modeled after NCHS’s National Health nInterview Survey, a national health survey of the civilian non-institutionalized npopulation of the United States. Depending on the definition used, the survey response nrate ranged from 43.6% to 71.4%. Negligible differences in the response rates were seen nwith respect to farm size and region of the state, although some non-random variation nin the response rates was apparent on a county-to-county basis. In attempting to assess nthe potential for non-response bias by conducting a (mail) survey of Phase-1 nonresponders, nresults indicated responders and non-responders were similar on most nfactors where direct comparisons were possible. Survey methods are described and nreasons for the lower-than-desired response discussed.