AMERICAN JOURNAL OF INDUSTRIAL MEDICINE 36:584±585 (1999)

Letter to the Editor

RE: Spontaneous Abortion in the BritishSemiconductor Industry

THE HSE STUDY

In the opinion of the undersigned, `̀ Spontaneous

Abortion in the British Semiconductor Industry: An HSE

Investigation'' [Elliott et al.] is a poorly designed and

ultimately uninformative study, with too small a study

population to yield any statistically reliable results. The

selection process used in this study failed to produce a

representative sample of semiconductor cleanroom workers.

Most of the test subjects had jobs outside the high-risk work

areas.

In a study of this type, to yield statistically reliable

results, a reasonable goal would be a study group of about

100 semiconductor production workers who had experi-

enced spontaneous abortions. The major U.S. studies that

the HSE study purports to counter had 113 and 187

cleanroom production workers who had experienced

spontaneous abortions when subjects in the study [Schenker

et al., 1995; Correa, et al., 1996]. The HSE study repeatedly

refers to results, all of which lack statistical reliability, based

on three or fewer cases of spontaneous abortion as proof of

no effect from cleanroom exposures to reproductive

hazards.

One of the reasons the HSE study was so small is that

the authors chose to exclude all women who had previously

had spontaneous abortions. Women with prior spontaneous

abortions are at higher risk and thus may well have been

those most sensitive and thus most likely to be affected by

an exposure. Their exclusion from the study could well have

biased the results.

The HSE authors obtained detailed work information

for only the ®rst three months of the workers' pregnancies.

Because the authors back-estimated the times of conception

using the actual birth dates of the offspring, the derived

conception times are rough estimates. Moreover, there may

have been additional exposures during the latter stages of

fetal development. Researchers usually evaluate potential

pre-birth exposures by obtaining work information several

months prior to estimated time of conception and through-

out the pregnancy.

The authors of the HSE study attempt to show that their

study results are consistent with other negative studies. The

few negative studies published in the United States have the

same problem as the HSE study, failure to design a study

with a study population large enough to yield statistically

reliable ®ndings [Schusterman et al., 1995; Gray, 1993;

Pinney and Lemasters, 1996].

The HSE study does produce one important fact. The

Final Report states that adequate monitoring of the workers'

exposures in cleanrooms does not exist in many of the U.K.

semiconductor plants. `̀ In this study exposures were

assessed primarily in a qualitative manner. This approach

was used because of the small quantity of personal exposure

data available on the large number of hazards under

investigation. Routine personal exposure sampling is

not often carried out in several of the semiconductor

plants in the study. At these plants air monitoring is only

carried out following a leak or spillage or following a

complaint about a smell [Elliott et al., 1998].'' This

admission strongly suggests that the level of occupational

health and safety in the U.K. semiconductor industry lags

behind that of other European countries, the United States

and Japan.

Finally, this article states that `̀ We found no reason to

suggest that any further speci®c action on the part of the

industry in Great Britain is indicated, nor have we identi®ed

any issues which currently warrant further research in the

British semiconductor industry.''

Because of the explosive growth of the semiconductor

industry and its importance to the economies of many

countries, all the studies conducted in the United States

concluded with recommendations for further research

efforts, and further workplace control measures. The

alarming ®ndings of a risk of spontaneous abortion in the

semiconductor industry raise additional questions about

cancer and other chronic diseases in the workers, and about

birth defects and other health problem in the children of

workers. The HSE has no scienti®c basis on which to

conclude that further research in the British semiconductor

industry is not warranted.

ß 1999Wiley-Liss, Inc.

Bruce Fowler, PhD

Toxicology Program

University of Maryland

Baltimore, MD

Joseph LaDou, MD

Division of Occupational and Environmental Medicine

University of California School of Medicine

San Francisco, CA

Ana Maria Osorio, MD, MPH

UCSF School of Medicine University of California

San Francisco, CA

Maureen Paul, MD, MPH

Occupational Health Program

University of Massachusetts

Worcester, MA

Shanna H. Swan, PhD

Department of Epidemiology

School of Public Health

University of California

Berkeley, CA

Daniel T. Teitelbaum, MD

University of Colorado School of Medicine

and Colorado School of Mines

REFERENCES

Correa A, Gray RH, Cohen R, et al. 1996. Ethylene glycol ethers andrisks of spontaneous abortion and subfertility. Am J Epidemiol143:707±717.

Elliott R, Jones J., McElvenny D, et al. 1998. Spontaneous abortion inthe UK semiconductor industry; an HSE investigation. Printed andpublished by the Health & Safety Executive, Epidemiology andMedical Statistics Unit, C160, 3/98.

Elliott RC, Jones JR, McElvenny DM, et al. 1999. Spontaneousabortion in the British semiconductor industry: an HSE investigation.Am J Ind Med 36:557±572.

Eskenasi B, Gola EE, Lesley BL, et al. 1995. Prospective monitoring ofearly fetal loss and clinical spontaneous abortion among femalesemiconductor workers. Am J Ind Med 28:833±846.

Gray R. 1993. Final Report. Retrospective and Prospective Studies ofReproductive Health among IBM Employees in SemiconductorManufacturing. Johns Hopkins University School of Hygiene andPublic Health, Baltimore, Maryland.

Pastides H, Calabrese EJ, Hosmer DW, Harris DR. 1998. Spontaneousabortion and general illness symptoms among semiconductor manu-facturers. J Occup Med 30:543±551.

Pinney SM, Lemasters GK. 1996. Spontaneous abortions and stillbirthsin semiconductor employees. Occup Hyg 2:387±401.

Schenker MB, Gold EB, Beaumont JJ, et al. 1995. Association ofspontaneous abortion and other reproductive effects with work in thesemiconductor industry. Am J Ind Med 28:639±659.

Shusterman D, Windham GC, Fenster L. 1993. Employment inelectronics manufacturing and risk of spontaneous abortion. J OccupMed 35:381±386.

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