Mercury

Epidemiological data

Administrative data

Endpoint:

epidemiological data

Type of information:

other: human data

Adequacy of study:

key study

Study period:

data from 1953 - 1978

Reliability:

other: reliable report; not rated acc. to Klimish

Rationale for reliability incl. deficiencies:

other: The epidemiological data reported is relevant for risk assessment.

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

publication

Title:

A mortality study of men exposed to elemental mercury.

Author:

Cragle, D.L.; et al.

Year:

1984

Bibliographic source:

J. Occup. Med. Nov. 26(11): 817-21

Materials and methods

Study type:

cross sectional study

Endpoint addressed:

carcinogenicity

Test guideline

Qualifier:

no guideline available

Principles of method if other than guideline:

Mortality and cancer indices were studied in a cohort of 2133 white men exposed to inorganic mercury vapours in an USA plant between 1953 and 1963 and followed up through the end of 1978. Death certificates were obtained from 371 of 378 workers who were reported to be deceased. Standard mortality rates (SMR) were calculated for a comparable unexposed worker population at the same plant.

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

Mercury dichloride

EC Number:

231-299-8

EC Name:

Mercury dichloride

Cas Number:

7487-94-7

IUPAC Name:

mercury dichloride

Details on test material:

- Name of test material (as cited in study report): elemental mercury vapours
No further information given.

Method

Type of population:

occupational

Ethical approval:

not specified

Details on study design:

METHOD OF DATA COLLECTION:
- Type: Record review / Work history

STUDY PERIOD: exposure period 1953 - 1963, follow-up until 1978

SETTING: occupational, USA

STUDY POPULATION:
- Total population (total no. of persons in cohort from which the subjects were drawn): 5,663 individuals (all white male employees who worked for at least 4 months between Jan. 1953 and April 1958).
- Selection criteria: white male workers in a Y-12 plant located in Oak Ridge, Tennesse, USA, (i) who were exposed to elemental mercury vapours between 1953 and 1963, and who were monitored by urinalysis for mercury exposure (mercury-exposed group) and (ii) non-monitored workers who were never at risk for mercury exposure (non-mercury exposed workers)
- Total number of subjects participating in study: 2,133 mercury exposed (monitored) subjects and 3,260 never at risk, non-exposed (not moniored) subjects.
- Sex/age/race: men, white Americans, ages not reported.

COMPARISON POPULATION:
- Type: state registry
- Details: age ajusted mortality experience of the U.S. white male population

HEALTH EFFECTS STUDIED
- Disease(s): underlying causes of death were coded to the eight revision of ICD; the mortality experience for each group was followed from Jan. 1953 or the date of hire.
- Death certificates were obtained from 371 of 378 workers who were reported to be deceased.
- Standard mortality rates (SMR) were calculated for a comparable unexposed worker population at the same plant.

Exposure assessment:

measured

Details on exposure:

TYPE OF EXPOSURE: Occupational exposure to elemental mercury vapours in a Y-12 plant located in Oak Ridge, Tennesse, USA. Elemental mercury was used in the lithium isotope separation process.

TYPE OF EXPOSURE MEASUREMENT:
(i) Biomonitoring (urine): A mercury urinalysis program statred in mid-1953; from 1954 on everone working in the mercury process was required to submit a specimen approxemately quaterly .
(ii) air-monitoring

EXPOSURE LEVELS:
(i) the plant action value (PAV) was set at 0.3 mg Hg/L urine; employees whose urine exceeded 0.6 mg Hg/L were removed from their work assignments until their levels fell below the PAV.
(ii) the highest air concentrations of mercury occured in 1955 and 1956 (up to 67.7 % of sample >0.10 mg/m3), see table 1

EXPOSURE PERIOD: The production process was placed in operation between December 1953 and Septemer 1955. The production doscontinued in 1963.

POSTEXPOSURE PERIOD: follow-up from 1963 to 1978

Statistical methods:

no data

Results and discussion

Results:

- Highest air concentrations (% of samples > 0.10 mg/m3) were measured in the years 1955/56 (max 87%) and declined until 1960 with percentage samples above 0.10 mg/m3 in the range 0.8 to max. 10%.
- In the mercury exposed and the non-mercury exposed groups, overall mortality rates were lower than expected. The number of observed cancers in each group was not significantly greater than expected based on US white male death rates.
- Incidences of both cancer of the lung (SMR = 1.34) and cancer of the brain and other CNS tissues (SMR = 2.30) were statistically significantly elevated in the non-mercury group. A higher SMR for lung cancer (SMR =1.34) was also observed in mercury workers, although not statistically significant.
- Selected categories and causes of death for the mercury workers who exceeded the “plant action value” (PAV) of 0.3 mg Hg/l urine (n=858) and for Hg workers who were exposed for one year and longer (n=1741) exhibited a significant deficit in the number of overall deaths when compared to the US white male population.
- Since excess of lung cancer was evident in both groups of workers, it is unlikely that they are related to mercury exposure.

Confounding factors:

Other factors than mercury present in the plant and other life-style factors.

Strengths and weaknesses:

no data

Any other information on results incl. tables

Numbers of observed (Obs) and expected (Exp) deaths for selected causes for the non-mercury workers and the mercury workers (incl. standardised mortality ratio SMR)

.	Non-mercury workers (n=3,260)			Mercury workers (n=2,133)
	Obs	Exp	SMR	Obs	Exp	SMR
All causes of death (001-998)	710	794.50	0.89	378	440.55	0.86
All malignant neoplasms (140-209)	175	159.22	1.10	85	90.82	0.94
All cancer of the liver (155, 156)	2	2.96	0.68	2	1.56	1.28
All cancer of the lung (162, 163)	71	52.93	1.34	42	31.36	1.34
Cancer of the kidney (189)	3	4.19	0.72	4	2.43	1.65
Cancer of the brain and other CNS (191, 192)	13	5.65	2.30	4	3.28	1.22
All disease of the nervous system and sense organs (320- 389)	5	6.86	0.73	2	3.84	0.52
All vascular lesions of the CNS (430-438)	36	46.36	0.78	24	24.03	1.00
All respiratory tract diseases (460-519)	37	43.52	0.85	18	23.98	0.75
Chronic nephritis (582)	3	4.19	0.72	1	2.09	0.48

 

Applicant's summary and conclusion

Conclusions:

Since excess of lung cancer was evident in both groups of workers (mercury exposed and non-mercury exposed), it is unlikely that they are related to mercury exposure. In conclusion, exposure to mercury vapours was not related to any excess of death from diseases or cancer of mercury target organs (liver, lung, brain, CNS and kidneys). No increases of incidences were found when level of exposure or length of exposure were considered.