Use of hazard Indices for a Theoretical Evaluation of Cigarette Smoke Composition

**Introduction:**

This text provides a comprehensive review of the use of hazard indices (hI) for evaluating cigarette smoke composition and its theoretical risk assessment. The reader will learn about the strengths and limitations of using this concept for risk assessment, consumer communication, ingredient assessment, and regulation of cigarette smoke and smokeless tobacco. The text also highlights the challenges in deriving quantitative risk estimates from the hI concept and the importance of considering the uncertainties and assumptions in the potency values used for the assessment.

**Key Points:**

* The hI concept has been applied to cigarette smoke and smokeless tobacco for determining and comparing theoretical lifetime risks, for consumer communication, for the prioritization of constituents for reduction, for ingredient assessment, and for the selection of constituents for regulation.
* The limitations of the hI approach include the limited number of MS constituents with available yield data, gaps and uncertainties in available potency values, application to relatively high exposure concentrations, and the default assumption of additivity.
* The derived TNhI is dominated by acrolein to an extent that there seems to be not much advantage in using the hI concept for noncancer assessments. The derived TChI is dominated by genotoxic carcinogens of the MS vapor phase and may thus complement currently used toxicological assays in a tiered evaluation approach.
* The hI concept is a theoretical concept and does not provide actual risk information. It should be applied with its limitations and weaknesses in mind, and its best application is for comparative purposes.
* The selection of smoke constituents for analysis and regulation should be based on risk assessment-based methods, taking into account the known animal and human toxicity, variation in constituent yields across brands, potential availability of technologies to reduce specific constituents, need to include constituents representing both the particulate and vapor phase of the smoke aerosol, need to include different chemical classes of constituents, and need to include constituents that would reflect not only cancer as a disease end point but also respiratory and cardiovascular disease end points.
* The application of the hI concept to cigarette smoke requires careful assessment and implementation, and the use of a hI-based approach for the control of unintended consequences is recommended.
* The hI concept has been used to identify potential risk reduction targets in the context of tobacco harm reduction, by prioritizing MS constituents based on analytical data from benchmark studies and potency values obtained from various authoritative bodies.
* The hI approach has also been applied to smokeless tobacco, but the application seems to be more of an exercise without added value compared to a simple chemical-analytical monitoring of NNK yields.

**Main Message:**

The hI concept is a useful tool for the risk assessment and regulation of cigarette smoke and smokeless tobacco, but it has limitations and uncertainties that should be carefully considered. The selection of smoke constituents for analysis and regulation should be based on risk assessment-based methods, taking into account various factors that would ensure the safety and public health benefits of the products. The application of the hI concept requires careful assessment and implementation, considering the uncertainties and assumptions in the potency values used for the assessment. In summary, the hI concept should be applied with caution and in a comparative manner, recognizing its strengths and limitations, to ensure the safety and public health benefits of tobacco products.

haussmann, hans-Juergen. “Use of hazard Indices for a Theoretical Evaluation of Cigarette Smoke Composition.” Chemical Research in Toxicology 25, no. 4 (april 16, 2012): 794–810. https://doi.org/10.1021/tx200536w.