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Tongji Medical College Huazhong University of Science and Technology. The 5th International Academic Conference on Environmental and Occupational Medicine. Long-term Exposure to Occupational Dust and Major Causes of Death in Chinese Workers. Weihong Chen, MD.

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Tongji Medical College

Huazhong University of Science and Technology

The 5th International Academic Conference on Environmental and Occupational Medicine

Long-term Exposure to Occupational Dust and Major Causes of Death in Chinese Workers

Weihong Chen, MD

MOE Key Lab of Environment and Health, Department of Occupational and Environmental Health, School of Public Health

  • Approximately 16.3% of industrial workers in China are exposed to various dust particles generated from production processes.
  • 3.0% workers exposed to silica dust.

Other occupational diseases

Chronic poisoning






Acute poisoning

Proportion of occupational disease in China (2005)


Approximately 10,000 new cases of pneumoconiosis were diagnosed a year.

The total number of pneumoconiosis cases at the end of 2008 was 638,234.


Health Effects


Long-term Dust exposure

Dose-response relationship




To examine the health effects of long-term exposure to occupational dust in manual workers in China.

design of research
Design of research

Study population

74040 workers

10 tungsten mines (32918)

6 iron and copper mines (18582)

4 tin mines (8243)

9 pottery factories (14297)

research subjects
Research subjects

Fixed cohorts: All workers actively employed between 1960 and 1974 and employed for at least 1 year in 29 mines or factories.




follow up
Follow up
  • The cohorts were followed for life status, diagnoses of pneumoconiosis, and work history to the end of 2003.
  • 83.78% of study subjects finished their employment in the end of 2003.
data collection
Data collection

1. Base information and occupational history

  • Personal information
  • Work history data
  • Smoking habit

Data collection

2. Data for vital status and health outcome

X-ray was taken every 3-5 years for dust-exposed workers even if they retired.

Diagnoses of pneumoconiosis: based on Chinese pneumoconiosis roentgen diagnostic criteria and comparison with ILO criteria.


Cause of death evidence

  • Level 1 - Medical record from a hospital or a personal doctor at a local hospital (60.5%)
  • Level 2 - Cause confirmed by employment register, accident record, or death certificate (35.2%)
  • Level 3 - Oral reports from relatives (4.3%)
data collection1
Data collection

3. Data for environmental exposure in workplaces

Historical environmental dust monitoring was started from 1950, 34,655 historical estimates were developed for 30 calendar-year periods (to 2003), using 2.8 million monitoring data points.

American measurements (NIOSH) did side by side dust samples with Chinese dust samples in 1988-89. Total dust, percent free silica and respirable dust were measured.

A facility, job title, calendar year exposure matrix was created base on above information.

data collection2
Data collection

3. Data for environmental exposure in workplaces

Environmental potential carcinogenic confounders were measured in 1988-1989 and 2003-2008.

  • 17 PAHs
  • The 30 elements: Al, As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Li, Mg, Mn, Mo, Ni, Pb, P, Pt, Se, Ag, Na, Sn, Te, Tl, Ti, W, V, Y, Zn, Zr.
  • Radon andγ-radiation determination
  • Asbestos and fiber determination
  • NO, SO2, CO
  • Dust exposure: employ in dust-exposed job titles and more than 6 month.
  • Cumulative dust exposure (CDE)
statistic analysis
Statistic Analysis
  • Hazard ratios(HR):Cox proportional-hazards regressions
  • The population attributable risk (PAR)


  • Standardized mortality ratio (SMR)

Expected number of death: mortality rates of the Chinese national population

the results dust exposure
The results- dust exposure

Annual Total Dust Concentrations, Averaged of All Job Categories in Different Mine/Factory in China, 1950-2003.


The mean percentage of crystalline silica in total dust

  • tungsten mines: 50% to 56%
  • tin mines: 27% to 38%
  • iron and copper mine: 7% to 15%
  • pottery factories: 30% to 35%
the results cohort
The results- cohort

1. Description of the Cohort


Average year of birth: 1937.11 ±11.1

  • Average year of hire: 1961.81±7.40
  • Males accounted for 92.5% of those exposed to dust.
  • The percent of cigarette smoking (former and current) was 61.16% among cohort members (98.8% for males) and 70.3% in dust-exposed workers (99.2% for males)
the results mortality
The results- mortality
  • The total mortality was 846.3 per 100,000 person-years
  • Dust-exposed workers: 978.4 per 100,000 person-years
  • Non-dust-exposed workers: 558.8 per 100,000 person-years
  • National mortality in 2008: 615.8 per 100,000 person-years
the results
The results-

The percentage of the cause of death in the cohort in end of 2003.

the results hr and cde
The results-HR and CDE

Hazard Ratios (HR) for Deaths Associated with Levels of Cumulative Dust Exposure (CDE)

the results smr
The results-SMR











Cause-specific SMR of Dust-Exposed Workers in the Cohort, By the End of Specific Years for Follow-Up, 1970-2003.
the results par
The results-PAR
  • After adjustment for age, gender, and smoking, dust exposure accounted for 15.0% of all deaths in this cohort.
  • The prevalence of silica dust-exposed workers was 1.7% among Chinese population in 2008. We estimated that a total of 43660 (95%CI, 35605 to 53307) deaths were attributable to occupational silica dust exposure in China.
the results incidence of pneumoconiosis
The results-incidence of pneumoconiosis
  • The incidence of pneumoconiosis was 7.0 per 1000 person-years (cumulative incidence, 21.8%) for dust-exposed workers.
  • tungsten miners: 10.1 (30.3%)
  • tin miners: 7.0 (22.0%)
  • iron and copper miners: 2.6 (7.5%)
  • pottery workers: 4.3 (13.3%)
  • long-term exposure to occupational dust was associated with substantially elevated mortality from cardiovascular disease, respiratory diseases, and pulmonary tuberculosis in those exposed workers in China.
  • These data underscore an urgent need for strengthen dust control in worksites.
next step
Next step
  • Separate analysis incidence of pneumoconiosis and its influence factors in different types of mine/factory.
  • The risk of lung cancer in each industry.
  • The mortality pattern among pneumoconiosis.

Jongqiong Chen (Tongji Medical College, China )

Zien Wu

Rongan Chen

Yaowei Liu

Haijiao Wang

Shaofan Weng

Yanfei Guo

Frank Hearl (DRDS and HELD, NIOSH, CDC, U.S.A)

William Wallace

Eva Hnizdo

Joseph McLaughlin (Occupational Epidemiology branch, NCI,U.S.A )

Mustafa Dosemeci

William Blot

Frank Bochmann (Institute for Occupational Safety and Health, HVBG,Germany

Yi Sun