Faculty of health sciences
School of Public Health
0204521g
dgresie@yahoo.co.uk;dgresie@hotmail.com / Ethylene oxide is used widely in hospitals as a gaseous sterilant for heat-sensitive medical
items, surgical instruments and other objects and fluids that come into contact with biological
tissues. Although ethylene oxide is recognised as a reproductive toxicant in humans, so far
few studies have been carried out to investigate the association between exposure to ethylene
oxide and the occurrence of adverse reproductive outcomes (Hemminki et al 1982 and 1983;
Rowland et al, 1996; Yakubova et al, 1976). The results of these studies suggested that
ethylene oxide is capable of causing reproductive dysfunction and that further research is
needed in order to understand its effects on reproductive health.
This study investigated the association between exposure to ethylene oxide during pregnancy
and adverse reproductive outcome in women sterilising staff working in sterilising units using
ethylene oxide in Gauteng province, South Africa.
The study had the following objectives: 1) to describe the extent and nature of ethylene oxide
use in sterilising units operational in medical facilities in Gauteng; 2) to assess the current
exposure to ethylene oxide in sterilising units in Gauteng; 3) to collect information on the last
recognised pregnancy using a questionnaire; 4) to assess the validity of the information on the
evolution and outcome of the last recognised pregnancy collected by the means of the
questionnaire; 5) to assess the association between occupational exposure to ethylene oxide
during pregnancy and adverse reproductive outcome.
The study population was represented by singleton pregnancies that: 1) occurred in women
currently working in sterilising units using ethylene oxide in Gauteng province, South Africa;
2) were the last recognised pregnancy occurring in these women after the 1st January 1992; 3)
occurred while the mother was employed. The adverse reproductive outcome was defined as
the occurrence of any the following: spontaneous abortion, still birth, pregnancy loss
(spontaneous abortion or still birth), low birth weight and combined adverse reproductive
outcome (spontaneous abortion, still birth or low birth weight).
The study enrolled 68.8% of the medical facilities in Gauteng that were using ethylene oxide
to sterilise medical equipment. The majority of the employees working in the sterilising units
included in the study were women (96.6%) and they were employed in one of the following
jobs: technician (operator), instrument packer and cleaner.
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Most of the sterilising units participating in the study used ethylene oxide sterilisation daily
and only 15.4% of them reported that the employees operating the ethylene oxide steriliser
used protective clothing. Recorded levels of ethylene oxide were provided by 46.2% of the
sterilising units; they were all bellow 0.25 ppm (the South African long-term exposure limit
for occupational exposure to ethylene oxide is 5 ppm). Changes in ethylene oxide sterilisation
equipment and or technology were reported by 42.3% of the sterilising units and they were all
engineering control measures aimed at reducing exposure to ethylene oxide.
Measurements of the current levels of ethylene oxide were performed at the time of the study
by the National Institute for Occupational Health using hydrobromic acid-coated petroleum
charcoal tubes connected to calibrated Gilian pumps through which air containing ethylene
oxide was drawn. The samples were analysed by the Analytical Services of the National
Institute for Occupational Health. A total of 418 samples were collected (100 blank samples,
97 personal samples and 221 static samples). Quality control was ensured by the following
methods: 1) verification by an Approved Inspection Authority; 2) collection of duplicate
samples; 3) collection of blank samples.
These measurements showed that exposure to ethylene oxide still occurred in sterilising units
(ethylene oxide was detected in 9 out of the 10 public hospitals) and that the employees most
exposed are the ones working with the ethylene oxide steriliser (technician or operator).
There were 113 women working in the sterilising units enrolled in the study who had been
pregnant after the 1st January 1992; 109 of them agreed to participate in the study and to
complete the questionnaire.
Information on exposure to ethylene oxide during pregnancy was obtained from three sources:
walk-through survey, questionnaire-collected data and measurements of the levels of ethylene
oxide in sterilising units at the time of the study.
Information on the evolution and outcome of these pregnancies was gathered from the mother
using a questionnaire.
The questionnaire collected demographic data, reproductive history, medical data, risk factors
for the adverse reproductive outcome (environmental and occupational exposures, lifestyle),
and data regarding the evolution and outcome of the last recognised pregnancy. The
questionnaire also collected detailed information on the job held at the time of the last
recognised pregnancy (if the woman was working with ethylene oxide, she was asked to
provide a complete list of daily tasks she was performing). Prior to administration, the
questionnaire was tested on a small sample of working women.
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The validity of the questionnaire-collected information on the evolution and outcome of the
last recognised pregnancy was assessed by comparing this information against medical
records (considered the “gold standard”). The assessment showed that mothers’ recall was
accurate for the following variables: medical facility were the pregnancy was recorded, date
of the reproductive event, gestation length, vital status of the newborn, number of foetuses,
child gender, disease/medical problems during pregnancy and treatment received during
pregnancy. There was an error in the mothers’ reporting of the birth weight of their babies.
The possible misclassification of outcome resulting from this error was shown to be nondifferential
(the proportion of subjects misclassified on outcome did not depend on exposure).
Therefore, this misclassification could bias the effect estimate towards the null value or it
could not produce any bias at all.
The analysis carried out to detect possible associations between exposure to ethylene oxide
and adverse reproductive outcomes included 98 of the initial 109 pregnancies on which
information had been collected (11 pregnancies were excluded from the analysis for the
following reasons: 2 were multiple pregnancies, 4 were conceived before 1st January 1992 and
5 were conceived while the mother was not employed).
Amongst the 98 singleton pregnancies included in the analysis, 19 were classified as exposed
and 79 as unexposed to ethylene oxide.
The relative risk for spontaneous abortion was RR=16.63 (95%CI=1.97-140.42; p=0.004), for
stillbirths RR=3.47 (95%CI=0.63-19.01; p=0.18), for pregnancy loss RR=6.24 (95%CI=1.95-
19.93; p=0.003), for low birth weight RR=0.61 (95%CI=0.09-4.30; p=0.51) and for combined
adverse reproductive outcome RR=2.09 (95%CI=1.00-4.36; p=0.06).
No confounders were detected for any of the associations between exposure to ethylene oxide
and the adverse reproductive outcomes under study.
For the association between exposure to ethylene oxide and combined adverse reproductive
outcome the analysis detected three effect modifiers: paternal age (father aged 40 or older at
conception), passive smoking and maternal age (mother aged 35 or older at conception).
In conclusion, this study, the first in South Africa on ethylene oxide exposure and adverse
reproductive outcomes, confirmed the widespread use of ethylene oxide, exposure to this
agent in public sector hospitals and associations between exposure to ethylene oxide and
spontaneous abortion and between exposure to ethylene oxide and pregnancy loss (either
spontaneous abortion or stillbirth).
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Moreover, the study provided data on reproductive outcomes in employed women (on which
scant data are available in South Africa) and added information on the validity of selfreported
pregnancy data relative to medical records.
The findings of the study support the conclusions of the previous studies that had suggested
that exposure to ethylene oxide during pregnancy could lead to adverse reproductive
outcomes. The study detected no associations between exposure to ethylene oxide and
stillbirth, low birth weight or between exposure to ethylene oxide and combined adverse
reproductive outcome.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/1616 |
| Date | 10 November 2006 |
| Creators | Gresie-Brusin, Florentina Daniela |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 981694 bytes, application/pdf, application/pdf |
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