Using noise exposure histories to quantify duration of vibration exposure in tree fallers.

A study of tree fallers in the British Columbia forest industry was done to determine if noise histories could be used to monitor the daily duration of exposure to hand-arm vibration from chain saws. Field observations and noise dosimetry showed that chain saw noise was distinguishable from other sound sources in fallers' work environments. Using data from noise dosimetry synchronized with observations of fallers' chain saw use, a model of sound pressure levels predictive of chain saw operating mode was developed. Subsequent workday noise histories of 13 fallers showed that the chain saw was off for an average of 331 +/- 27 min, idling for 91 +/- 11 min, and cutting wood for 96 +/- 7 min. This method could be used to collect data to refine dose-response estimates for vibration syndrome or to monitor administrative controls of vibration exposure time.

Longitudinal study of vibration-induced white finger among coastal fallers in British Columbia.

Symptom-based vibration-induced white finger was determined longitudinally from a questionnaire administered to 71 full-time fallers exposed 2-4 h daily to generally heavy (greater than 11 kg), large displacement (greater than 95 cc) chain saws. The prevalence of Raynaud's phenomenon among 55 fallers (after 16 fallers were excluded because of possible confounders) was 51% in 1979-1980. This figure did not differ significantly from the prevalence in 1984-1985 (53%). Among the 28 fallers reporting symptoms in 1979-1980, seven reported no symptoms in 1984-1985, while four indicated improvement in the severity of symptoms resulting in a decreased stage assessment. Evidence for actual recovery was weak because of discrepancies in the symptom reporting. Reported recovery and improvement in the group with symptoms in 1979-1980 was counterbalanced by a significant 30% onset of new symptoms among fallers who were asymptomatic in 1979-1980. Six of the eight fallers reporting new symptoms were exposed only to antivibration saws, a finding suggesting that the type of saws used in the present investigation is not preventing the onset of new disease. Weighted 4-h equivalent acceleration levels from the handlebars of saws commonly used by the cohort group in 1984 ranged from 4.0 to 12.4 m/s2.

Blood lead and carboxyhemoglobin levels in chainsaw operators.

Fallers in the British Columbia west coast lumber industry often work in climatic and local conditions where little ventilation in their immediate environment is possible. Under these conditions carbon monoxide (CO) and lead fumes from exhaust gases could build up and become a serious occupational hazard. This study monitored the environmental exposure of six fallers to carbon monoxide, nitrogen oxides, and lead under conditions where buildup of these agents would be expected. At the same time blood samples were taken to correlate these environmental concentrations to carboxyhemoglobin (COHb) and blood lead levels. Although there was a highly significant difference between the fallers and the controls regarding the exposure to CO and lead as well as their corresponding COHb and blood lead levels, the environmental and blood concentration of the agents in question did not exceed the maximum allowable concentrations. Temporary short fluctuations in carboxyhemoglobin levels were not monitored in this study and cannot be ruled out as a potential occupational hazard.

Vibration-induced white finger among selected underground rock drillers in British Columbia.

Ninety-five rock drillers who used pneumatic hand-held drills were interviewed and tested. Thirty-seven were excluded because of factors predisposing to the appearance of white fingers other than exposure to industrial hand-drill vibration. Forty-five percent of the remaining 58 drillers suffered from periodic attacks of Raynaud's phenomenon. Symptoms were present in 25% of the drillers exposed for 1-5 years and in 80% of those exposed for greater than or equal to 16 years. Nine percent of the cases were classified as severe. The median latency for the onset of the blanching symptoms was 7.5 years. The prevalence of Raynaud's phenomenon was 4% among a reference group of 56 miners not exposed to hand vibration and corrected for possible predisposing factors. Objective evidence indicated delayed finger rewarming after a combination of digital ischemia and cooling in 75% of the drillers with blanching symptoms and 18% of the referents without symptoms. There was evidence of an increased frequency of vibration-induced white finger among current cigarette smokers. Weighted 4-h equivalent acceleration levels measured from the handles of 26 jack-leg and 13 stoper drills from the same mines as the miners ranged from 15 to 32 m/s2. These levels exceed recommended guidelines of the International Organization for Standardization.

Vibration white finger disease among tree fellers in British columbia.

On the basis of symptomatology, 51% of 146 fellers from seven coastal lumber camps in British Columbia were found to be suffering from vibration white finger disease (VWFD). Symptoms were present in 70% of the men who had been engaged in felling for 11 to 15 years and in 75% of the men who had been employed in this occupation for more than 20 years. Prevalence rates were not changed by the exclusion of 57 fellers with a history of vibration exposure other than the chain saw, or with a history of other possible secondary causes. The prevalence of symptoms in an age-corrected control group was 2%. There was objective evidence of disease (delayed finger rewarming after cooling) in 31 of the 43 fellers with symptoms (72%) and in 13 of the 74 controls (18%) without symptoms. The median latency period for fellers with symptomatic VWFD was 7.3 years. There was no evidence that the condition was related to cigarette smoking.