DEHP changes brain enzyme at very low levels
DEHP increases allergic response in mice at low levels
Phthalates linked to genital abnormalities in boys
linked to preterm birth
levels in children
linked to sperm damage
and reduced sperm count
call for more research on phthalates
Listen to an international teleconference
with scientists discussing phthalate health risks
are phthalates and how are they used?
What are the health concerns?
The debate about regulation and public health
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What are phthalates? How are they used?
Phthalates are a class of widely used industrial compounds known technically as dialkyl or alkyl aryl esters of 1,2-benzenedicarboxylic acid. There are many phthalates with many uses, and just as many toxicological properties.
Phthalates crept into widespread use over the last several decades because of their many beneficial chemical properties. Now they are ubiquitous, not just in the products in which they are intentionally used, but also as contaminants in just about anything. About a billion pounds per year are produced worldwide.
Intentional uses of phthalates include softeners of plastics, oily substances in perfumes, additives to hairsprays, lubricants and wood finishers. That new car smell, which becomes especially pungent after the car has been sitting in the sun for a few hours, is partly the pungent odor of phthalates volatilizing from a hot plastic dashboard. In the evening's cool they then condense out of the inside air of the car to form an oily coating on the inside of the windshield.
are the health concerns?
Much of the existing literature on phthalates' toxicological properties
focuses on the old approach to toxicology: high level exposure for
cancer endpoints, and occupational exposure leading to adult infertility.
In the past several years, however, particularly led by Earl Gray's
laboratory at the US Environmental Protection Agency, attention
has turned to low-dose toxicity of phthalates during crucial windows
of fetal development. As these studies have advanced, they have
fundamentally changed our perception of potential health risks of
According to Hauser et al. (2006): "Phthalates are a class of multifunctional chemicals used in a variety of consumer and personal care products. Highmolecular- weight phthalates (eg, di-2-ethylhexyl phthalate --DEHP-- and butylbenzyl phthalate --BBzP--) are primarily used as plasticizers in the manufacture of flexible vinyl, which is used in consumer products, flooring and wall coverings, food contact applications, and medical devices. Manufacturers use low-molecular-weight phthalates (eg, diethyl phthalate --DEP-- and dibutyl phthalate --DBP-) in personal care products (eg, perfumes, lotions, cosmetics), as solvents and plasticizers for cellulose acetate, and in making lacquers, varnishes, and coatings, including those used to provide timed release in some pharmaceuticals."
high doses of phthalates do constitute risks in the sense of traditional
toxicology, these low doses change the stakes dramatically. Gray's
work reveals that male reproductive development is acutely sensitive
to some phthalates. For example, the phthalates dibutyl phthalate
(DBP) and diethylhexyl phthalate (DEHP) produced dramatic changes
in male sexual characteristics when exposure took place in utero,
at levels far beneath those of previous toxicological concern. These
changes included increases in the rates of hypospadias
and other indications of demasculinization.
questions about phthalates have been raised during the last few
years for the National Toxicology Program, under the auspices of
its recently established "Center for the Evaluation of Risks
to Human Reproduction" (CERHR), to convene a panel of independent
experts in 1999 to review scientific evidence addressing developmental
threats of phthalates. The panel issued a draft
report in August 2000. Its conclusions are severely restricted
by the fact that few of studies necessary to address fetal impacts
of phthalates have been done. For a least one of the phthalates
they addressed, DEHP, the panel had serious concern about health
impacts. Not surprisingly, given the state of research the report's
conclusions are tentative, establishing plausible but uncertain
risk. One of the key points is DEHP's impact on developing Sertoli
cells, cells in the male reproductive tract that are central to
sperm formation. Damaged Sertoli cells during development lead to
sperm maladies in adulthood, including low
sperm count. DEHP does not cause Sertoli damage directly; damage
instead is caused by a metabolite of DEHP, monoethylhexyl phthalate
In summer 2006, two papers upped the ante considerably on possible low-level effects of phthalates. The ranges at which Gray et al. have conducted their experiments are close to the range of common human exposure, but still somewhat above. These new papers reveal biological impacts in animals well within the range of common human exposure, and show show non-monotonic action of DEHP at environmentally-relevant levels. One examined impacts on the activity of the enzyme aromatase, which is essential for masculinizing male brains. The second experimented with DEHP's ability to exacerbate allergic reactions to an allergen, providing a possible clue as to why allergy rates have gone up so much in the developed world. Non-monotonic dose response curves are important because they invalidate current approaches to developing health standards.
In May 2005: For the first time, researchers have identified an association between pregnant women’s exposure to phthalates and adverse effects on genital development in their male children. The pattern of genital changes seen in these baby boys is consistent with the "phthalate syndrome" previously observed in rodents prenatally exposed to phthalates. It is also suggestive of "testicular dysgenesis syndrome," a human health condition proposed to be linked to exposure to endocrine-disrupting compounds. The adverse effects are seen at phthalate levels below those found in one-quarter of women in the United States, based on a nation-wide survey by the Centers for Disease Control. More...
August 2000, Puerto Rican scientists reported
on an association between exposure to DEHP and premature breast
development in young girls, possibly linking phthalates to trends
September 2000, the US Centers for Disease Control released the
first substantial assessment
of phthalate exposure in the American public. Their study analyzed
urine metabolite residues of seven phthalates. Levels were high
for several of the compounds studied, particularly the metabolite
of DBP. Of greatest concern was the discovery that in their sample,
an disproportionate number of women of child-bearing age bore high
levels of this metabolite. Given Gray's data on fetal vulnerability,
this is precisely the population that should minimize exposure to
winter/spring 2002-2003, three studies linked phthalate exposure
to reductions in semen quality. All were of men exposed to background,
environmental levels of phthalates, not higher occupational levels.
One showed DNA
damage in sperm. Two others (one
from the US, the other
from India) found reductions in sperm quality in men with slightly
elevated phthalate levels. Phthalate levels associated with the
damage were well within the range experienced by many Americans.
debate about regulation and public health protection
Over the past several years, debate has grown in the regulatory
world about what to do about phthalates. Industry argues that years
of phthalate use without visible harm prove product safety. Critics
counter that animal studies establish plausible risk but that the
relevant human epidemiological studies focused specifically on the
impacts of fetal exposure simply haven't been done. They point,
moreover, to the fact that human health endpoints consistent with
phthalate damage are found in animal experiments. They also point
out that certain exposures, particularly those associated with children
chewing on soft polyvinyl chloride toys and patients receiving intravenous
medication through polyvinyl chloride equipment may lead to very
high exposures. [The CDC report, above, adds to that list of high
exposure concern: the fetuses of pregnant women using cosmetics
regulators kicked off this debate
when they began to explore the possibility of bans on toys intended
for infants that contained DEHP. This set in motion fierce industry
lobbying from the United States to head off the ban, an effort that
not only proved unsuccessful ultimately in Europe, but one that
was matched in the US by a call by the Consumer Products Safety
Commission for a voluntary phase-out by US manufacturers, not only
from pacifiers and toys but also from certain medical devices. Several
large US toy manufacturers, including Disney and Mattel, made public
commitments supporting the phase-out.
debate heated up further in the US when an industry PR firm that
masquerades as a public health organization, the American Council
on Science and Health, put together a panel to review the safety
of phthalates. Headed by retired Surgeon General C. Everett Koop,
the panel ultimately issued a flawed report that concluded phthalates
were safe. Their report failed to consider several key recent publications
and misrepresented another, citing the latter as stating that no
kidney damage was caused when in fact the research did not assess
kidney damage. They committed an even more basic error, moreover,
by accepting the absence of data as proof of safety. Absence
of data proves only ignorance. A devastating critique of this report
was published by Health
Care Without Harm (a PDF file; long download on slow modems).
American Academy of Pediatrics entered the debate in June 2003,
a report in Pediatrics that recommends research on
phthalates effects on the fetus and infants. Their review of the
literature found that no studies had directly addressed this issue,
yet animal research clearly documents harm and data from the US
Centers for Disease Control shows widespread exposure.