Association of occupational noise exposure, bilateral hearing loss with hypertension among Chinese workers.

OBJECTIVE: To evaluate the relationship of occupational noise, bilateral hearing loss with blood pressure and hypertension among a Chinese population. METHODS: We included 15 422 individuals from a cross-sectional survey of the key occupational diseases in 2017 in Wuhan, Hubei Province, China. Occupational noise exposure was evaluated through workplace noise level and/or the job titles. Hearing loss was defined as a pure-tone average of 25 dB or higher at speech frequency (0.5, 1, 2 kHz) or high frequency (3, 4, 6 kHz) in both ears. Hypertension was defined as blood pressure at least 140/90 mmHg or self-reported current use of antihypertensive medication. RESULTS: Compared with participants without occupational noise exposure, the prevalence of hypertension was significantly higher for noise exposure duration of 5 to less than 10 years [odds ratio (OR) = 1.13, 95% confidence interval (CI) = 1.04-1.27] and at least 10 years (OR = 1.17, 95% CI = 1.09-1.30). In the sex-specific analysis, the association was significantly pronounced in male (OR = 1.18, 95% CI = 1.06-1.32 for duration of 5 to <10 years; OR = 1.25, 95% CI = 1.12-1.38 for duration ≥10 years), but not in female (OR = 1.01, 95% CI = 0.80-1.11 for duration of 5 to <10 years; OR = 1.06, 95% CI = 0.90-1.20 for duration ≥10 years). In the subsample analyses, bilateral hearing loss was associated with a higher prevalence of hypertension, no matter for speech frequency hearing loss (OR = 1.12, 95% CI = 1.02-1.30 for mild; OR = 1.35, 95% CI = 1.20-1.50 for severe) or for high-frequency hearing loss (OR = 1.24, 95% CI = 1.03-1.50 for mild; OR = 2.40, 95% CI = 1.80-3.17 for severe). The sex-subgroup analysis of hearing loss with hypertension was similar as occupational noise and hypertension. CONCLUSION: Our study has suggested occupational noise exposure is a potential risk factor for hypertension.

[Comparative field study on high flow rate samplers for respirable fraction-A solution to smaller collected masses].

OBJECTIVE: Dust sample mass gain is too smaller to satisfy the limit of detection (LOD) even in most cases during dust sampling at workplaces nowdays, especially for respirable fraction. Therefore, it is aimed to solve the problem by increasing sample load with high flow rate samplers. METHODS: In A and B two shipyards respirable welding fume was sampled by high flow rate cyclone samplers of FSP-10 (10 L/min) for 2-2.5 hours and normal flow rate FSP-2 (2 L/min) for 3-4 hours with a stratigy of parallele sampling at the same workpalce, in order to compare their mass gain, coincidence rate with LOD, and airborn dust concentration. RESULTS: Sample mass gain of 0.97±0.40 mg and 1.61±0.86 mg respectively in the two factories by FSP-10 was significantly higher than that of 0.29±0.12 mg and 0.51±0.27 mg by FSP-2 (t-test, P<0.05 in both cases) , increasing herewith the coincidence rate with LOD from 26.8% (when sampling with FSP-2, calculated together with samples of the two factories) to 89.7%. However there was no significant difference in dust concentrations by the two different samplers, 0.53±1.88 vs 0.73±1.61 mg/m(3) by FSP-2 and FSP-10 in the shipyard A and 1.14±1.78 vs 1.01±1.63 mg/m(3) in the factory B (t-test, P>0.05 in every case) . In addtion, sample loading by FSP-2 was found to be correlated to sampling time (R(2)=0.7906, y=0.002 6x) , therefore, it has to sample for ≥192.3 min to meet the LOD (0.5 mg) in case of normal flow rate. CONCLUSION: By using of high flow rate cyclone FSP-10 the problem of LOD could be solved, along with increased sample mass and similar respirable dust concentration by the two samplers. Some techincal improvements of FSP-10 and increasing of LOD coincidence rate by other methods was also disscussed.

Re-characterization of some factors influencing aerosol sampling in the workplace: results from field studies.

OBJECTIVE: Workplace aerosol sampling is challenged by its influencing factors and methodological limitations. Some factors, including blank setting, electrostatic effect, sample mass gain, and limit of detection (LOD), were studied to characterize them further and thereby to improve the sampling method. METHODS: Through a field sampling in two shipyards and by an analysis of a large amount of dust data from different industries, the influencing factors were comparatively studied with emphasis on their effect on the final result. RESULTS: After calibration with field blanks, the concentrations of most sample types in the shipyards decreased significantly, varying by as much as -24.3% of the final measurements. After laboratory blank calibration, dust concentrations increased or decreased without a definite change trend. With a variation of -1.8%, only the measurements of Chinese "total dust" sampled with polypropylene filters were significantly influenced by the electrostatic effect. The LOD coincidence rate was only 17.3% for American respirable dust in different industries and 12.2% for respirable particles collected by normal flow rate samplers (FSP2) in the shipyards. The latter increased to 73.9% when high flow samplers (FSP10) were used. CONCLUSIONS: It was suggested that field blank calibration was the predominant influencing factor in comparison with electrostatic effect and laboratory blank adjustment. The LOD coincidence rate was too low for reliable sampling, and this might be improved by use of high flow samplers.

A comparative field study on dust measurements by different sampling methods with emphasis on estimating factors for recalculation from chinese 'total dust' measurements to respirable dust concentrations.

In China, dust samplers were originally designed to collect 'total dust' for a short term during production, which is different from the widely adopted sampling strategy for dust. With the aim to provide the conversion factor from Chinese total dust to US and German respirable dust and to look at the influences on conversion factors from environment, production, and instruments, a comparative field study on the dust concentration measurements by different sampling methods was carried out in the same Chinese industries as in the 1989-1990 study and in some other factories. A supplemental experiment was also conducted in a wind tunnel. Dust concentration was measured with a parallel sampling strategy by using the following samplers: 10-mm nylon cyclone for US respirable dust (AR), FSP-Berufsgenossenschaftliches Institut für Arbeitssicherheit (BIA) cyclone for German respirable dust (GR), and samplers for Chinese total dust (CT). Totally, 1434 samples were collected (269 AR, 198 GR, and 967 CT), from which 429 matched sample pairs (249 pairs of AR/CT, 180 GR/CT) were available to calculate conversion ratios. Industry- and job-based conversion factors are presented in this study. The conversion factor of AR/CT was 0.38 for tungsten mines, 0.19 for copper/iron mines, 0.65 for tin mines, and 0.20 for pottery industry, while the factor of GR/CT was 0.69 for tungsten, 0.37 for copper/iron, and 0.52 for pottery. In the job category, AR/CT factors varied from 0.16 to 0.96 and GR/CT from 0.12 to 0.72. For the industries studied in 1988-1989, the AR/CT and GR/CT factors were 0.29 and 0.45, respectively. Both factors were definitely influenced by production, CT dust concentration, sample gain, and variation of dust concentration. Moreover, the respirable dust concentration by FSP-BIA was significantly higher than that by 10-mm cyclones, 63.27-73.10% more as showed also by the wind tunnel experiment. Meanwhile, the GR/CT ratio was significantly larger than the AR/CT in every industry or job with only few exceptions. The GR/CT estimates should be considered as independent ones. Following these results, there is a need to use 'ideal samplers' (consistent with the internationally accepted respirable fraction) in practice and to assess the existent samplers in order to homogenize the exposure data situation.