Handbook of Solvents - George Wypych - ChemTech - Ventech!

20.3 Pregnancy outcome following solvent exposure 1347
20.3.5 A PROACTIVE APPROACH FOR THE EVALUATION OF FETAL
SAFETY IN CHEMICAL INDUSTRIES
[Adapted, by permission from K.I. McMartin and G. Koren, Teratology, 60, 130 (1999)
Copyright 1999 John Wiley & Sons, Inc. Reprinted by permission of Wiley-Liss, Inc. a division
of John Wiley & Sons, Inc.]
Introduction
Women, their families and employers are concerned about potential fetal risks that may be
associated with occupational exposure to chemicals. To be able to assess such risks in a particular
plant, one has to quantify local exposure and contrast it with evidence-based literature
data. There are, however, numerous obstacles that prevent such risk assessment from
being routinely performed. In the reproductive literature there are few studies that actually
quantify exposure levels. In the instance where authors attempt to quantify or stratify exposure,
the exposure frequencies and the exposure doses are inconsistent between studies.
For many chemicals one can measure neither airborne nor blood levels. Smelling the
odor of organic solvents is not indicative of a significant exposure as the olfactory nerve can
detect levels lower than several parts per billion, which are not necessarily associated with
toxicity. Odor thresholds for some solvents are far below several parts per million (ppm).
Examples of some odor thresholds 33 include carbon disulfide (0.001 ppm vs. TLV-TWA
(skin) [Threshold Limit Value-Time Weighted Average] 10 ppm), acetaldehyde (0.03 ppm
vs. TLV-TWA 25 ppm), and ethyl mercaptan (2x10 -5 ppm vs. TLV-TWA 0.5 ppm). 34 In the
workplace, exposure is usually to several chemicals that may change between working days
or even within a single day. The amounts of chemicals absorbed are often unknown, and the
circumstances of exposure may vary from workplace to workplace or even within the same
operation.
Typically, investigations into fetal safety are induced by single or clusters of specific
malformations, or by symptoms in exposed women. We recently reported a proactive consultation
process where, for a selected chemical compound to which women working in the
Products and Chemicals Divisions at Imperial Oil Limited (IOL) may be exposed, actual
exposure data were contrasted with literature values and a risk assessment was constructed.
35
Methods
An agent inventory list was used to analyze the component (the name of material or agent),
exposure group, the number of employees within an exposure group, and the routine rating
factor for routine work. Exposure group is defined as a group of employees who have similar
exposures to chemical, physical, and/or biological agents when: 1) holding different jobs
but working continuously in the same area (e.g., process workers), or 2) holding unique
jobs in an area or moving frequently between areas (e.g., maintenance workers). The routine
rating factor for routine work (work which is part of the normal repetitive duty for an exposure
group) is defined as follows:
Rating Factor (RF) Definition
0 No reasonable chance for exposure
1-5 Minimal, exposure not expected to exceed 10% of the
occupational exposure limit (OEL)
6-9 Some daily routine exposures may be expected between
10% and 50% of the OEL
10-15 Some daily routine exposures may exceed 50% of the OEL