Study of Lead Effects at Low Levels Could Affect EPA Regulations

From 9-17-10 Inside EPA, an article on a new analysis planned of health
impacts of low-level lead exposure.
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NTP Study Of Low-Level Lead Health Effects Could Drive EPA Regulations

The National Toxicology Program (NTP) is developing an analysis of the
current scientific evidence surrounding the human health risks of lead at
extremely low levels, particularly reproductive effects, an analysis that
could drive a host of new EPA regulations governing air emissions, lead
dust, drinking water and other environmental releases of the metal.

The National Institute of Occupational Safety and Health (NIOSH), which
intends to use NTP’s conclusions when considering new recommended exposure
limits (RELs) for workers, requested that NTP’s Center for the Evaluation of
Risks to Human Reproduction (CERHR) conduct the analysis in 2007 to address
the disconnect between its current occupational exposure limits of 40
micrograms per deciliter (ug/dL) in adult workers, including women of
child-bearing age, and data showing adverse effects in children at much
lower levels, a NIOSH source says.

The Center for Disease Control & Prevention (CDC) considers a blood lead
level of 10 ug/dL to be an elevated level of concern in children, but
acknowledges that adverse effects have occurred at lower levels, saying
there may not be a safe threshold level for blood lead in children, and the
CERHR source says studies may indicate that levels below 10 ug/dL could be
of substantial concern to adults as well. [snip]

NTP announced in an Aug. 23 Federal Register notice that it is collecting
information about ongoing studies or upcoming publications on lead exposures
lower than 10 ug/dL for consideration in the evaluation, and asked for
nominations of science advisers to an ad hoc panel to conduct a peer review
of the pending monograph.

In addition to developing a weight of evidence framework for pinpointing
adverse health effects at low level lead exposures, the monograph will also
seek to identify vulnerable lifestages for such exposures, specific blood
lead levels associated with particular endpoints, whether additional
biomarkers, such as bone lead, are associated with the effect, and how those
biomarkers may be linked to the blood lead level.

The CERHR source says the monograph will address a “full suite of effects”
besides reproductive endpoints, including renal toxicity, hypertension,
dental caries, and neurotoxic effects to “provide clarity where there are
the most questions.”

The focus of the evaluation, which should be published by spring or early
summer of 2011, will consider only human epidemiological data concerning
levels at or below 10 ug/dL, and seek to identify a low enough blood lead
level to serve as a sort of control group, a difficult task since nearly
everyone in the population has some degree of blood lead, the CERHR source
says.

“We don’t really see a level of lead that’s safe,” the NIOSH source says.
[snip]

A science advisory panel said in July that EPA’s planned approach for
assessing risks and limiting exposure to lead paint dust in private
residences and in developing the safety rules for commercial buildings,
undercut risk because they failed to take into account reproductive and
developmental endpoints at low blood lead levels. [snip]

— Bridget DiCosmo
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The Federal Register notice is available at
http://frwebgate1.access.gpo.gov/cgi-bin/TEXTgate.cgi?WAISdocID=mhXuDK/4/1/0&WAISaction=retrieve.