Di-2-ethylhexyl phthalate (DEHP), one of the most abundant phthalates
produced, has been incorporated into flexible plastic products such as
food containers and packaging, toys, medical equipment, and home and
garden products. DEHP is being phased out of some products because of
growing concern about its potential health effects. A French team has
now established the first tangible link between one phthalate, the DEHP
metabolite mono-2-ethylhexyl phthalate (MEHP), and altered human germ
cell development
[
EHP 117:32–37; Lambrot et al.].
The French team acquired testes from morphologically normal fetuses
of women undergoing legal abortion during weeks 7 to 12 of gestation.
Using an organotypic culture system, they exposed the testes for 3 days
to one of three concentrations of MEHP: 10–6, 10–5, or 10–4
M. The highest concentration was 2 orders of magnitude higher than that
known by the authors to occur in humans; the lowest was the same order
of magnitude as that found in human milk in Finland, which reached
1,410 µg/L. Biomonitoring data for 2005 published by the Centers for
Disease Control and Prevention (CDC) showed that MEHP in the urine of
U.S. residents reached 52.1 µg/L (or 10–8 M).
At the highest concentration, the authors found that exposure
reduced germ cell numbers by 40%. The sharp reduction occurred via an
increase in apoptosis, or programmed cell death, without any effect on
proliferation. The authors note that the plunge in numbers is crucial
because the germ cells formed during fetal life—which will go on to
become ova or sperm—help determine adult fertility.
The highest concentration of MEHP also significantly reduced the
messenger RNA expression of anti-Müllerian hormone, which plays a key
role in the development of certain cells into male reproductive organs,
usually during week 8 of fetal development. The lowest concentration of
MEHP tested didn’t show adverse effects for the pathways analyzed.
The general population is routinely exposed to many types of
phthalates, with at least one metabolite, monoethyl phthalate,
documented in urine by the CDC at concentrations of 10–6
M. The authors suggest that researchers should investigate additional
phthalates and interactive effects, other concentrations and periods of
exposure, different time periods of fetal development, and additional
pathways. They also note that their findings conflict with some results
from animal studies. For instance, there were no MEHP effects on
testosterone production in this study, but testosterone suppression has
occurred in rats exposed to phthalates. Such discrepancies may be due
to differences between species, they say.
Originally published at ehponline.org
