The New York Times (NYT) article is
discussing a recent publication in the journal Environmental Health
Perspectives related to “Project TENDR”, which stands for “Targeting
Environmental Neuro-Developmental Risks”. In the NYT piece, statements of the
Project TENDR group presented in the published paper are summarized and it is
pointed out that this publication comes at the same time as the signing into
law of the overhaul of the Toxic Substances Control Act (TSCA). The reporter
states that the TENDR group wants the chemical industry to prove that a
chemical is safe before it is marketed, in place of U.S. Environmental
Protection Agency’s (EPA) authority to review all chemicals in commerce as
stipulated under the updated TSCA law.
Unfortunately, the NYT’s article on the
TENDR statement lacks scientific basis and is out of date. The reporter failed to discuss
specific things that the new TSCA law accomplished, and how they relate to many
of the concerns raised by the TENDR group. A prime example is that under the
new law EPA will review all new chemicals and make an affirmative determination
before they are allowed to enter commerce. In addition, all chemicals in
commerce in the United States now will undergo a risk-based review by EPA for
the first time. The EPA will be prioritizing chemicals for review, and there are
strict deadlines that must be met by EPA in order to ensure compliance by
chemical manufacturers. EPA will no
longer consider costs and benefits when making a decision about the safety of a
chemical; only health and environmental safety will be considered. Most
importantly with respect to the issues raised by Project TENDR, EPA must
consider whether vulnerable groups such as infants, pregnant women,children, the elderly, will be exposed to a chemical and, if exposure is expected to occur, then the risks
to those specific groups must be assessed. Unfortunately, these provisions of the TSCA
overhaul are not mentioned in the NYT piece, even though these changes to the existing
regulatory system will require that both existing chemicals and new chemicals
undergo scrutiny to determine if they might pose a risk to the brain of the
developing organism.
The list of compounds described in the
article and highlighted in the TENDR consensus statement includes some compounds
well-recognized to pose a risk to neurodevelopment precisely because of the
chemical testing and evaluation that was required as part of existing EPA regulations,
an important point that is missing in the NYT article. For example,
organophosphate pesticides have been around for many decades and have been
required to undergo EPA registration since enactment of Unites States law in
1947 (i.e.., Federal Insecticide,
Fungicide and Rodenticide Act or FIFRA). Similarly, among the other chemicals
mentioned, lead, mercury and PCBs are already extensively regulated, while air
contaminants such as PAHs, nitrogen dioxide and particulate matter are also specifically
regulated under current programs at EPA. With all of the existing EPA programs, as science has advanced in
our understanding of the process of human development and risks to infants and
children, the testing of chemicals has evolved. Over the last 20 years,
specific advances in chemical testing and risk assessment requirements by EPA have
focused on risks to infants and children within the auspices of FIFRA, the
Clean Air Act, and even generally with implementation of the program to examine
endocrine-disrupting effects of chemicals in commerce. As a result, it is hard
to understand how the TENDR consensus can use such examples as evidence that
the current regulatory system “is fundamentally broken”. In fact, with
enactment of TSCA reform, EPA has the tools it needs to review both new and
existing chemicals, with a requirement to focus on risks to vulnerable
populations such as infants and children.
Unfortunately, when discussing the issue
of chemical exposure and risks to the developing organism, the fundamental
principle of toxicology that underpins the effects that chemicals can have on
living organisms, dose-response, is often ignored or even not considered. It is
the dose of the chemical, and the pattern of exposure, that determines whether
a chemical produces an adverse effect on an organism, not simply the presence
of a chemical, even for developmental neurotoxicity. Just as a critical
concentration at the site of action is needed before a drug can produce its
beneficial effects in humans, the same principle applies to toxicity produced
by any chemical. Effects that might be reported at high doses will not occur at
lower doses if the concentration at the site of action falls below the
threshold for toxicity. Evidence-based toxicology and epidemiology dictates
that the dose of chemical is the critical factor when examining the risk posed
by a chemical, not just its presence, even in the human body. Given that many
of the epidemiological studies investigating the relationship between exposure
to specific chemicals and conditions such as autism and ADHD, and referred to
in the NYT article and the TENDR consensus statement, often suffer from a lack
of exposure information during critical periods of development, any conclusions
that can be drawn from such studies are limited by the lack of dose-response
information.
Although the issues of autism and
attention-deficit hyperactivity disorder (ADHD) are clearly issues of concern in
medicine today, improvements in diagnostic methods and criteria for such
diseases are acknowledged by the TENDR group to account for part of the
purported increase in different forms of developmental neurotoxicity. When
considered in light of the changes in TSCA that are now signed into law, there
is no scientific basis for the assertion that the system in the United States
is “fundamentally broken” as stated by the TENDR group. Instead, with new
scientific developments in our understanding of the processes that regulate
neurodevelopment in humans, and the new emphasis on risks posed to vulnerable
human populations as part of chemical risk assessment at EPA, the regulatory system
in place going forward should prevent the occurrence of the types of
compound-specific problems (e.g.,
widespread lead exposure through air, food, and water) encountered in the last
century.
