Ralph, Monona:
Contaminants of variable or unknown composition are a potential problem for all in the EHS professional community, but MORE important is multiple chemical exposures since in real life, no one is ever exposed only to one toxicant at a time.
No realistic framework is yet established for accounting for the multiple contaminant exposures to derive an acceptable exposure range. Industrial hygienists use a fractional limit approach that all acknowledge as too simplistic:
Dose = Conc. 1 + Conc. 2 + Conc. 3 + . . . Conc. i
Dose 1 Dose 2 Dose 3 Dose I
While this approach can estimate the cumulative dose for multiple contaminants, it is really only applicable to those contaminants with similar toxic endpoints.
A better approach for both issues may be control banding to estimate potential hazards and identify appropriate control methods to reduce the hazards, but control banding cannot identify whether the exposures are “acceptable”. (Note that no “safe” levels can be identified for many contaminants.)
Ralph A. Froehlich, CIH, CSP, QEP
Helix Environmental, Inc.
(937) 776-8435 cell
Thanks, Ralph. It's about time this problem is addressed. Monona
-----Original Message-----
From: Ralph Stuart <ralph**At_Symbol_Here**RSTUARTCIH.ORG>
To: DCHAS-L**At_Symbol_Here**Princeton.EDU
Sent: Wed, Mar 1, 2023 2:00 pm
Subject: [DCHAS-L] The Next Frontier of Environmental Unknowns: Substances of Unknown or Variable Composition, Complex Reaction Products, or Biological Materials (UVCBs)
While I was randomly surfing the web, I ran across the article below from last May in ES&T about the data challenges of working with materials with unknown or variable compositions. Among other aspects of this challenge, the authors (at least one of whom is a CHAS member) discuss working with risk data when the constituents of a particular pollutant are unknown. They also provide an extensive literature review (178 references) to provide an overview of the relevant work in the field. With the situation in East Palestine still developing, many of the chemical safety information issues discussed in this article are worth considering.
On the less technical side, there is also an interesting article describing the business leadership lessons that could be learned from the East Palestine event in Forbes at
- Ralph
The Next Frontier of Environmental Unknowns: Substances of Unknown or Variable Composition, Complex Reaction Products, or Biological Materials (UVCBs)
Substances of unknown or variable composition, complex reaction products, or biological materials (UVCBs) are over 70 000 “complex” chemical mixtures produced and used at significant levels worldwide. Due to their unknown or variable composition, applying chemical assessments originally developed for individual compounds to UVCBs is challenging, which impedes sound management of these substances. Across the analytical sciences, toxicology, cheminformatics, and regulatory practice, new approaches addressing specific aspects of UVCB assessment are being developed, albeit in a fragmented manner. This review attempts to convey the “big picture” of the state of the art in dealing with UVCBs by holistically examining UVCB characterization and chemical identity representation, as well as hazard, exposure, and risk assessment. Overall, information gaps on chemical identities underpin the fundamental challenges concerning UVCBs, and better reporting and substance characteri!
zation efforts are needed to support subsequent chemical assessments. To this end, an information level scheme for improved UVCB data collection and management within databases is proposed. The development of UVCB testing shows early progress, in line with three main methods: whole substance, known constituents, and fraction profiling. For toxicity assessment, one option is a whole-mixture testing approach. If the identities of (many) constituents are known, grouping, read across, and mixture toxicity modeling represent complementary approaches to overcome data gaps in toxicity assessment. This review highlights continued needs for concerted efforts from all stakeholders to ensure proper assessment and sound management of UVCBs.
Ralph Stuart, CIH, CCHO
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