P.56
SRA
2014
Exposure Assessments for
Contaminants of Emerging Concern
Greene CW, Shubat PJ • Minnesota Department of Health • Saint Paul, Minnesota
www.health.state.mn.us/cec
Non-deliberate
self-exposure
A chemical may have a beneficial effect on the body when consumed purposefully.
Beneficial exposures
(targeted)
A chemical may have a beneficial effect on the body when consumed without knowledge or intent for any beneficial effect.
Beneficial exposures
(non-targeted)
There are some chemicals whose presence in or on a person provides a tangible
health benefit, but that benefit is not related to the person’s exposure.
Beneficial effects
(non-exposure-related)
A chemical may have new applications or uses that indicate increasing human exposure in the future.
Exposure potential trending up (new uses)
Exposure potential may be decreasing due to reduced use stemming from economic or regulatory forces.
Exposure potential trending
down (new restrictions)
A chemical may have no non-water exposures for most of the population,
but very high exposures for a small number of people.
* Not a Contaminant of Emerging Concern, but evaluated as a test case for computer-based modeling of exposure. For nursing mothers taking prescription
medications, MDH has advised concerned
individuals to ask a physician about ways
to minimize exposure. For other chemical
products, MDH advises carefully following
label instructions to avoid unnecessary
exposure, and only using products when
needed.
Examples
Effects on HBV
Messaging
Examples
Effects on HBV
Messaging
Examples
Effects on HBV
Messaging
Examples
Examples
Effects on HBV
Messaging
Examples
Effects on HBV
Examples
Effects on HBV
Venlafaxine/Desvenlafaxine
Triclosan
TCEP
Sulfamethoxazole
Sulfamethazine
Pyraclostrobin
Microcystin-LR
Metribuzin & degradates
Manganese*
Isobutanol
DEET
1,4-Dioxane
Diethylhexyl phthalate
Dibutyl phtahlate
"Outlier" exposures
(bimodal)
For venlafaxine and desvenlafaxine, MDH
used an RSC of 0.8 because prescription
use is the only potential non-water
exposure source. For infant exposure, we
relied on studies indicating no adverse
effects in nursing infants whose mothers
were taking the medications. MDH informs the public on how they may
be unknowingly exposed to this chemical,
what the potential risks may be, and how
to avoid or reduce exposure.
Exposures based on consumption for
beneficial effect (such as a medication)
are considered outside the scope of the
RSC calculation. Potential drinking water
exposures are far below exposures
deriving from medicinal uses.
MDH describes beneficial effects when advising the public on potential
exposures. If drinking water is a potential
source of exposure, MDH can recommend
practices that can minimize exposure.
MDH describes beneficial effects when
advising the public on potential
exposures.
"Outlier" exposures (bimodal)
Exposure potential trending up (new uses)
Isobutanol: This biofuel is considered a potential growth industry in Minnesota
due to perceived advantages over ethanol.
At the time of review, there was one
production facility operating in the state.
Anticipated changes in use do not directly
affect guidance values, but may increase
the likelihood that a chemical will undergo
review.
Potential new or expanded uses of a CEC
are communicated to the public along
with current exposure information.
Exposure potential trending down
Bisphenol A: Regulatory changes enacted
in the past few years may result in
reduced exposure from some routes in the
future.
If future data indicate that a chemical's exposure potential from non-water
sources was negligible, a higher RSC
value could be used. In the case of
Bisphenol A, new regulations only affect a
small portion of overall BPA use, and no
data on the effects of recent regulations
were available at the time of review.
In its chemical information sheets, MDH
informs the public of regulations that may
reduce certain sources of exposure.
Examples
A chemical can enter a person’s body without the person knowingly taking the chemical internally or applying it to
the body. These chemicals may be present in household dust, food, home furnishings, or household chemicals.
Beneficial effects (non-exposure-related)
Venlafaxine and desvenlafaxine: Infants are exposed to these antidepressants at 4
to 8 percent of the maternal dose, a level
not considered to be harmful to the infant,
but which exceeds the MDH RfD. The
infant benefits from his or her mother’s
exposure because it reduces maternal
depression and improves maternal
attentiveness and engagement with her
newborn.
For an essential nutrient found at elevated
levels in source water, guidance values for
water are influenced by known or
estimated dietary exposures at all life
stages.
Microcystin-LR: Most people are not
exposed at all. A small number of people
have exposures due to dietary
supplements or unsafe swimming
practices, and these exposures are often
very high relative to the RfD.
Effects on HBV
Deliberate
self-exposure
Manganese, which is a concern for well
water in some parts of Minnesota, is also
an essential nutrient found in food. It was
evaluated in a test case for application of
computer models to exposure
assessment.
Chemicals in this category have been
assessed without regard to the "outlier"
exposures, which can be more effectively
controlled through educating the public
on the potential hazards of exposure. In the case of Microcystin-LR, an RSC of
0.8 was applied.
Messaging
For some chemicals, particularly drugs, the only significant source of exposure
(aside from potential drinking water exposures) is deliberate intake.
The impact on the RSC value depends on
the magnitude of exposure relative to the
RfD, and the potential for the chemical to
be in drinking water. Biomonitoring data
and exposure modeling can be used to
estimate exposures.
Sulfamethoxazole, carbamazepine,
venlafaxine, desvenlafaxine: For these
prescription drugs, exposure to
individuals taking the drug are not
included in general population exposure
estimates. Non-prescription exposures
are not likely to occur. Therefore, an RSC
of 0.8 has been used for drinking water
exposures.
Examples
(our evolving list)
Most CECs, with the exception of
medications, fit into this category.
Effects on HBV
MDH communicates both the relative levels of exposure of infants and adults,
and the potential health significance of
known levels of exposure.
Beneficial exposures (non-targeted)
Messaging
Children/infant exposures exceed adult exposures
When a relatively small number of people
have high exposures due to overuse of a
chemical or product, MDH advises people
to follow product label instructions and
avoid using products when they are not
needed. For triclosan, MDH states that
cleaning products containing triclosan are
no more effective than regular soap and
water.
Bisphenol A, benzyl butyl phthalate,
dibutyl phthalate, diethylhexyl phthalate:
For these chemicals found in plastic
products and house dust, infants and
children are particularly susceptible, and
studies indicate that their exposures are
higher than those of older children or
adults. MDH water guidance for acute and short
term exposures is based on an infant
water intake rate, and for nonvolatile
chemicals, the default RSC is 0.5 (rather
than 0.2) because infants experience a
narrower range of exposure environments
than adults. When infant exposures equal
or exceed adult exposures, this
assumption fails, and MDH uses an RSC
of 0.2 for all durations.
Beneficial exposures (targeted)
Messaging
For many CECs we find that infant exposure equals or exceeds those of older children or adults.
MDH advises people to follow instructions
and labels when using medications or
products that involve self-exposure to
chemicals.
Triclosan: Published studies indicate that
heavy users of products containing
triclosan (soaps, cleaning products, dental
care items) may be exposed at levels
approaching the RfD. Microcystin: For most people, exposure to
harmful levels of microcystin is not likely.
However, a person taking algae-based
dietary supplements or who swims in a
lake with an algal bloom may easily be
exposed at levels exceeding the RfD.
If high levels of exposure only affect a
small portion of the population, and
drinking water exposures are low, MDH
generally does not base the RSC on the
highly exposed individuals, because
lowering the drinking water guidance
value would do little to reduce exposures.
Non-deliberate self-exposure
Examples
Elevated risk
at upper percentile
For this mode of exposure, water may not
be the primary concern. When possible,
MDH offers advice on how to minimize
non-water exposures.
Effects on HBV
For many CECs, especially those in consumer products, exposure varies widely. For some of these chemicals, individuals
at the high end of the distribution have exposures that approach the MDH toxicological reference dose.
Messaging
Ubiquitous Exposure,
elevated risk
Examples
For some CECs, human exposure is very common from non-water sources, and many people may be expected to
have exposures that meet or exceed a level that would be a health concern.
If this is the only source of exposure aside
from potential drinking water exposure,
the RSC may be raised to 0.8 if the
exposure is well-controlled (such as for
prescription drugs). In cases where
exposure is not as well controlled (e.g.,
acetaminophen and DEET), an RSC of 0.2
was used.
Effects on HBV
Modes of
Exposure Ubiquitous Exposure, low risk
Sulfamethoxazole: Available data indicate
that prescription use is the only likely
exposure source.
Acetaminophen: Medicinal use is the most
likely exposure source, but the level of
concern is somewhat higher than for
prescription medications because of the
wide range of OTC formulations, including
many intended for infant use. DEET: Exposures are highly variable, and
many formulations are available that
exceed MDH guidelines for potency.
Messaging
For some CECs that are common in consumer products, human exposure at low levels is
nearly universal, and these exposures are far below the MDH RfD value.
Cadmium
MDH produces information sheets that describe,
in plain language, the likelihood of exposure,
potential health risks from drinking water
and other sources, anf how to avoid or reduce
exposure.
Bisphenol A
Communication
Benzyl Butyl Phthalate
3
MDH applies a Relative Source
Contribution (RSC) factor to allocate risk
among multiple sources.
Acrylamide
2
•
Which modes of exposure apply?
• How do water and non-water
exposures compare to one
another, and to the toxicological
reference dose (RfD)?
• Chemical use
• Environmental sources
If exposure comes from non-water sources,
the drinking water RSC may be lowered in
order to allocate more of the RfD to nonwater sources. However, a 20% floor is
used. If drinking water is not an important
exposure source, a very low RSC will not
do much to help reduce human exposure. Deliberate self-exposure
Acetaminophen
1
Characterization
Investigation
MDH informs the public about potential
exposure routes, and while not
recommending any actions be taken,
suggests ways in which a person could
reduce his or her exposure if they are
concerned.
Effects on HBV
Guidance Values
When general population exposures are
very low, it would be possible to allocate
more of the RfD to drinking water by
using a high RSC (0.8). However, in cases
where drinking water exposures are
already low, MDH has opted not to do
this, and instead used default values (0.2
or 0.5).
Acrylamide: Widespread dietary exposure
to acrylamide is well established in the
literature, and levels of exposure amount to
a substantial fraction of the MDH RfD. More
importantly, dietary exposures are far in
excess of an exposure level that
corresponds to a 1 10-5 excess cancer risk.
We therefore used a low RSC (0.2) for all
exposure durations.
Children/Infant exp. exceed adult exp.
Elevated risk at upper percentile
Ubiquitous exposure, elevated risk
Messaging
In evaluating exposures to
CECs over the past four years, MDH has looked for patterns
that could be used to better characterize chemicals reviewed in the future. The modes of exposure presented below represent some of the
exposure types that have differentiated
CECs from each other, and from tradi
tional contaminants. New CECs, evaluated after being
nominated by stakehol
ders and ranked based on exposure and toxici
ty concerns, can be
classified in terms o
f these
modes o
f exposure,
and possibly add new information to
further refine the process. MDH is currently in the process of integrating computer-based exposure modeling into this
process. A special project to identify a set of modeling tools and procedures was
completed earlier this year, and these models have been applied to some aspects of
human exposure and fate and transport modeling of CECs.
Examples
env
ironment and in the human body. Exposure from non-drinking water routes may in some
cases approach or exceed the toxicological reference dose (RfD). A
t
the same time, for many CECs, drinking water exposure is not the primary exposure
concern. MDH uses a Relative Source Contribution (RSC) factor to allocate only a portion of the RfD
to
drinking water exposure. Sel
ecting an RSC is a qualitative
process informed by
quantitative measurements (such as measured and modeled exposure estimates), as well
as
by policy-based decisi
ons. Our exposure assessment
process i
s used to determi
ne an
appropriate RSC va
l
ue and communicate exposure and risk information to the
public.
Chlorpyrifos (& CP Oxon)
The Minnesota Department of Health develops human health-based values (HBVs) for
chemicals in drinking water. In 2009, MDH expanded its work to include “
Contaminants of Emerging Concern”
(CECs)-- chemicals which lack current guidance or have new and
changing health risk information. The modes of exposure to CECs differ from those of “traditional
”
contam
inants. Infants
may
be exposed more than adults; people are often exposed to CECs through deliberate action-taking medications or us
ng
i
consumer products; and some CECs are ubiquitous in the
Effects on HBV
Discussion
Background
Bisphenol A, phthalates: Exposure studies
based on biomonitoring and/or intake
estimates were available. Estimates of
general population and upper percentile
exposures were far below the MDH RfD
values.
Messaging
Ubiquitous exposure, low risk
Carbamazepine
second
summary
MDH conducts exposure assessments for contaminants of emerging concern in
drinking water. We are developing a framework to assess CECs in terms of
common modes of exposure, in order to judiciously allocate potential health risks
to multiple exposure sources and communicate potential risks to the public.
Messaging
[email protected]
MDH advises the public on how to avoid
the "outlier" exposures.