Objectives: To investigate the occupational and genetic risk factors inducing lumbar disc degeneration in a Chinese population, and to explore their synergistic interactions. Methods: A case-control study involving 178 low back pain patients with lumbar disc degeneration and 284 controls was carried out. Five types of work-related factors were investigated using questionnaires. Polymerase chain reaction and restriction fragments length polymorphism was used to detect the polymorphisms of MMP-3 (matrix metalloproteinase-3)(rs731236), VDR-Taq (vitamin D receptor-Taq) and VDR-Apa (vitamin D receptor-Apa)(rs35068180). Rothman's synergy index was used to measure the synergistic interactions between gene polymorphisms and occupational risk factors. Results: Family history of lumbar disc diseases, back injury history, whole-body vibration, bending/twisting, heavy physical workload, age, mutation alleles 5A of MMP-3 and A of VDR-Apa were significantly associated with lumbar disc degeneration (OR=12. 70, 11.79, 8.96, 5.46, 1.05, 1.96 and 1.70, respectively, p<0.05). Synergistic interactions existed between the mutation allele 5A of MMP-3 and wholebody vibration exposure, the mutation allele 5A of MMP-3 and bending/twisting, and the mutation allele A of VDR-Apa and bending/twisting (SI=13.27, 2.91, 2.35, respectively, p<0.05). Conclusions: The results of this study suggest that gene-occupation interaction might play a certain role in exaggerating lumbar disc degeneration. There is a possibility that subjects who carry mutation alleles 5A of MMP-3 and/or A of VDRApa are more vulnerable to lumbar disc degeneration when they are exposed to whole-body vibration and/or bending/twisting under ergonomic loads. It is estimated that 15% to 20% of adults have back pain during a single year, and 50% to 80% experience at least one episode of back pain during their lifetime 1) . Jin 2) reported that the incidence of low-back pain (LBP) was as high as 50% in an investigation of one population of Chinese workers. Lumbar disc degeneration is considered to be a primary cause of LBP 3,4) . The pathogenesis of lumbar disc degeneration includes radial fissures, rim tears in the annulus, and loss of water content in the nucleus pulpous and annulus. These changes are suspected of underlying many back pain symptoms.The etiology of lumbar disc degeneration is complex, and recent research on the causes of disc degeneration have shed light upon a better understanding of the risk factors contributing to disc degeneration. Magora 5) suggested that occupational factors contributing to the acceleration of spinal degeneration included heavy physical loads, manual materials handling consisting of lifting, bending and twisting, prolonged sitting, sustained non-neutral work postures, and vehicle driving. Videman 6) confirmed that occupational exposures are viewed as the primary source of the mechanical factors

Musculoskeletal disorders and related risk factors in machinery manufacturing were investigated using interviews, postural analysis, and the revised National Institute for Occupational Safety & Health lifting equation. Sixty-nine workers involved in manual materials handling (Job A) and 51 machinery workers less involved with manual material-handling tasks (Job B) were studied. Low back pain (LBP) (at least one episode lasting for 24 hours or more in past 12 months) prevalence rates were 63.8% and 37.3% for Jobs A and B, respectively. Prevalence rates of LBP every day for a week or more attributed to lifting were 26.09% and 5.88% for Jobs A and B, respectively. Multiple regression analysis revealed that lifting repetitiveness and work age contributed to the occurrence of LBP. The "composite load" (object weight x activity repetitiveness) had a significant adverse effect on LBP.

The aim of this study was to evaluate the lung disorders of the workers exposed to rush smear dust. A cross sectional study was carried out on 1,709 current workers (788 male, 921 female) in 80 factories. All subjects were asked by questionnaire, and health examination including chest Xray was conducted for 661 workers in 35 factories. Lung function test was also examined for 119 non-smoking males among 661 subjects. Dust samplings were collected and total and respirable dust concentrations at 127 spots in 35 factories were measured. The geometric mean dust concentration in the workshops was up to 20.00 mg/m 3 , and the geometric mean respirable dust concentration reached 8.22 mg/m 3 . The mean quartz concentration of accumulated dust was 29.2%. The prevalence of radiographic small opacities profusion category > or = 1/0, according to the ILO 1980 Classification System, was 2.6% among 661 employees. One worker was found to have pneumoconiotic findings of 2/2 profusion accompanied with large opacity. The prevalence of pneumoconiosis (1/0 or more) correlated with cumulative dust exposure (r=0.192, p<0.0001). The similar relationship was found between the prevalence rate of cough or sputa and worksite dust concentration. In non-smokers, a positive association was found between the prevalence of cough and occupational exposure duration (r=0.080, p=0.004). Approximately 19.3% and 34.5% of employees suffered from respiratory impairment for FVC and FEV1.0, respectively. This is the first report of "rush" pneumoconiosis in China. Rush mat workers were found to be at high risk for pneumoconiosis, a preventable disease. Our results showed a dose-response relationship between rush-mat dust level and the prevalence of pneumoconiosis. Similar relationship between the prevalence of cough and sputum and the work duration was found for non-smoking workers but not for smoking workers.