The political will in the European Union to enact REACh was
and is extraordinary. The body politic in the EU wants this
regulation and certainly needs it to be effective. It should be clear that it
cannot be effective if the exposure assessment half of the risk equation used
for REACh is faulty. Underestimation of exposure and risk hurts people's health directly,
over-estimations hurts people's well-being by unnecessary hurting of the
economy. The use of good modelling tools is critical or REACh, in my opinion,
will ultimately be doomed to fail.
I have always thought that first principle physical chemical
models (FPModels) have been superior to models that are not based on first principles
(NFPModels). Now a thoughtful and talented Danish
researcher (Dr. Antti Joonas Koivisto) is examining and demonstrating with logic and DATA exactly
why first principle models are better and, most likely, even necessary to make good regulatory
decisions.
An early question might be:
Why develop NFPModels when FPModels are available for development? The easy and probably correct answer: They can be developed relatively quickly and
with less effort and expense. FPModels are available but need to be
parameterized for critical exposure scenarios and that means research dollars.
NFPModels, for the most part, are based on dimensionless
factors to calculate scores, which are then converted to exposure values. They are conceptual models
than do not have to conform to first-principles and are thus (using Joonas' word) somewhat vague.
While there are other NFPModels, the big hitter in the EU for
modelling exposure via REACh appears to be Stoffenmanager® v.7.1 which as of last month:
·
is reportedly validated by 15 scientific studies
based on more than 6000 measurements.
·
has more than 33,000 users with 50 new users
per week.
·
used to make over 200,000 regulatory decisions
It is accepted by the Dutch Labour inspectorate as a
validated method to evaluate exposure to hazardous substances in the
workplace. More important, the European
Commission officially recognises Stoffenmanager as a instrument to comply with
the REACh regulation.
Other REACh-recommended NFPModels include:
ECETOC TRA
MEASE
EMK-EXPO-TOOL
ART
Although
somewhat varied in their approach, they all share the same feature that they
are
all based on dimensionless factors to calculate scores, which
are then converted to exposure values.
They are conceptual models than do not have to conform to
first-principles (like the conservation of mass). Thus, they are not scientifically formalized and that leaves them difficult
to explain.
Dr. Koivisto
asserts, and I agree, that there should be minimum requirements for regulatory
exposure models and that those criteria should be no less than the Daubert
criteria used in US Courts for valid scientific testimony. The model criteria:
- Is applicable and has been tested.
- Has been subjected to peer review and is
generally accepted.
- The rate of error is known and acceptable.
- The existence and maintenance of standards and
controls concerning the operation.
- Is generally accepted in the relevant
scientific community.
Joonas
goes on to advise that FPMmodels are superior to the above NFPModels (what he
calls “imaginary” models) because:
• Mass
flows are traceable à Model
can be used for environmental, occupational and consumer exposure assessment!!
• There
is No unit conversions!!
• Error
analysis can be made separately for emission source, emission controls, and
dispersion.
• No need
for Tier levels; the Tier level depends
on available information.
• Possible
”calibration” is straight forward (e.g. chamber tests)
• In the
NF/FF model the NF volume and air mixing are adjustable according to the source
(free parameterization).
• Results
are easy to interpret
• TRANSPARENT!
• Easy to
develop for further needs
• No need
to discretize parameters (e.g. room size, ventilation rate,…)
• Accuracy
superior when compared to compared to mechanistic or conceptual modes
I took
most of the above from a November 29, 2018 presentation that Joonas gave in
Denmark. I will be happy to send the
PowerPoint slide deck of that talk to anyone who asks at mjayjock@gmail.com.