Kieselguhr, soda ash flux-calcined

Health surveillance data

Administrative data

Endpoint:

health surveillance data

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: Study with major shortcomings (e.g. no information about smoking habits, asbestos exposure)

Data source

Reference

Reference Type:

publication

Title:

A 26-year radiographic follow-up of workers in a diatomite mine and mill

Author:

Cooper WC, Sargent EN

Year:

1984

Bibliographic source:

J Occup Med. 1984 Jun;26(6):456-60; PMID: 6330326

Materials and methods

Study type:

health record from industry

Endpoint addressed:

repeated dose toxicity: inhalation

Test guideline

Qualifier:

no guideline available

Principles of method if other than guideline:

Chest roentgenograms of 473 employees of a California diatomite plant were reviewed as part of periodic re-evaluation of the efficacy of the dust control program.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Kieselguhr, soda ash flux-calcined

EC Number:

272-489-0

EC Name:

Kieselguhr, soda ash flux-calcined

Cas Number:

68855-54-9

Molecular formula:

SiO2

IUPAC Name:

silanedione

Details on test material:

- Name of test material (as cited in study report): diatomaceous earth, diatomite (flux-calcinated)

Method

Type of population:

occupational

Ethical approval:

no

Details on study design:

STUDY POPULATION
- Total study population: 577
- Selection criteria: only workers with at least 4 years of service were examined
- Total number of subjects participating in study: 473
- Sex/age/race: males and females, in service from 5 to 39 years
- Smoker/non-smoker: no information on smoking habits are provided

METHOD OF DATA COLLECTION
Chest roentgenograms were taken during the period July 1, 1974 through June 30, 1979

STUDY PERIOD: from July 1, 1974 through June 30, 1979 as follow-up of earlier evaluations in 1953, 1963, 1969, and 1974

SETTING: The study was conducted among the workforces of the John-Mansville diatomaceous earth (DE) mining and processing plant in Lompoc, California.

HEALTH EFFECTS STUDIED
- Disease(s): pneumoconiosis
- Classification: International labour organisation (ILO) U/C classification system

Results and discussion

Results:

The distribution of film classification is shown in table 1. There were 24 (5.1%) in the doubtful category (0/1 or 1/0) with 11 (2.3%) in categories that would be considered with pneumoconiosis (i.e. 1/1 or greater). This contrasts with the earlier findings of 6.8% in the doubtful category and 4.7% in the positive category in 1974. The fact that there were only 6 individuals classified as 1/2 or higher is noteworthy. There were 19 such cases in 1974. No large opacities were reported. Both rounded (40%) and irregular (60%) small opacities were noted. The distribution was as follows: p=5, q=9, s=11 and t=10. For those of 1/1 profusion or greater, the predominant small opacities were p=2, s=2, and t=7.
In 21 individuals pleural changes were reported. In five of these, it was limited to costophrenic angle obliteration, three being unilateral and two bilateral. In 11 other individuals, circumscribed or diffuse pleural thickening was suspected but not definitely identified. In five cases there were reports of definite circumscribed or diffuse thickening; in three workers these finding could be associated with a previous thoracotomy, tuberculosis and asbestos exposure, respectively.
There were 119 participants in the original survey of 1953 still employed as of July 1, 1974, and 74 employed as of July 1, 1979 (table 2). Only 5 of the 479 individuals with negative films in 1953 have subsequently been reported as having a film consistent with pneumoconiosis (1/1 or more). Of the 52 with doubtful films in 1953, 44 had subsequent follow-up films. 23 had had their last follow-up films interpreted as negative, 20 as doubtful and only one as definitely positive (1/2). Of the 22 workers with definite pneumoconiosis in 1952, 20 had follow-up films. 4 were described as negative through their final films, 11 showed no progression and 5 showed progression.

Any other information on results incl. tables

Table 1: Film classification in 473 current and terminated employees with five or more years of service:

Years of service	No.	Film classification
		Negative	Doubtful (1/0 or 0/1)	Positive (1/1 and higher)
5-9	72	70	1	1^a)
10-14	99	94	5	-
15-19	108	106	2	-
20-24	82	75	6	1^a)
25-29	63	56	4	3
30-34	38	30	5	3
35-39	5	4	-	1
40-44	2	1	1	-
45-49	4	2	-	2
Total	473	438	24	11
%	100	92.6	5.1	2.3

^a)Changes present on pre-employment film

 

Table 2: Participants in the 1953 survey available for review as of successive follow-up dates

Classification	1953	No follow-up	1963	1969	1974	1979
Negative	479	204	147	128	104	66
Doubtful	52	8	25	13	7	5
Definite
- Simle	29	2	14	9	6	3
- Confluent	26	4	17	8	2	0
Total	586	218	203	158	119	74

 

Applicant's summary and conclusion

Conclusions:

11 of 473 employees examined (2.3%) had films classified 1/1 or higher and only 6 of these were categorized1/2 or more. All of the latter had more than 25 years of service. The presence of only two examples of suspected large opacities (0.4%) was in marked contrast with 1953 when 4.4% of films showed coalescent lesions.

Executive summary:

Chest roentgenograms of 473 employees of a diatomite plant were reviewed as part of periodic re-evaluation of the efficacy of the dust control program. The plant’s processing of diatomite included flux-calcination, which provided opportunities for exposure to cristobalite. The films examined were those of workers with at least 5 years of service. Only 11 films were interpreted as showing changes consistent with pneumoconiosis, i.e. small opacities of profusion categorized as 1/1 or greater. Only six were classified as ½ or more. All who developed categories 1/1 or higher during their employment had more than 25 years of service. No large opacities were reported. The low prevalence and the absence of definite pneumoconiosis in employees with fewer than 25 years of service was in striking contrast with findings in 1953. At that time more than 25% of those with 5 or more years of employment had roentgenographic evidence of pneumoconiosis and over 10% had confluent changes producing large opacities.