Formaldehyde Exposure Modeling Science Series: Part I
This posting is the first of a three-part series on formaldehyde emissions from hardwood plywood (HWPW), medium-density fiberboard (MDF), and particleboard (PB), collectively called composite wood products. This series will focus on the benefits of applying computer modeling tools to the interpretation of formaldehyde emission data, and subsequent risk management decisions. Part 1 of this series provides an overview of the new U.S. EPA formaldehyde emissions standards and explains how computational exposure modeling was used in the agency cost-benefit analysis. The remaining parts of this series will explain the factors that affect formaldehyde emissions from composite wood products and our recommendations for how computational modeling can be used to help stakeholders interpret emission testing results.
Part 1: U.S. EPA Formaldehyde Emission Standard Highlights the Importance of Exposure Modeling in Rule Implementation
The pre-publication version of U.S. EPA's Emission Standards for Composite Wood Products' final rule was posted on July 27, 2016, as Title VI of the Toxic Substance and Control Act (TSCA), with most provisions expected to become effective in the summer of 2017. U.S. EPA's rule focuses on reducing exposures to formaldehyde, and avoidance of adverse health effects. Although rarely a focus of most media reports, U.S. EPA frequently relies on complex modeling and cost-benefit analysis to support a conclusion that total quantified benefits outweigh costs. U.S. EPA's formaldehyde rulemaking relied on the use of modeled estimates of formaldehyde exposure to calculate hypothetical benefits quantified by a willingness to pay to avoid eye irritation and the number of cases of nasopharyngeal cancer.
The U.S. EPA Emission Standards for Composite Wood Products applies to all types of HWPW, MDF, PB, and finished products that are sold, supplied, or manufactured in the United States. The requirements of the Standard are consistent and coordinated with the similar California Air Resources Board (CARB) Airborne Toxic Control Measure (ATCM). The key points of the rule include:
• Producers of composite wood products within the scope of the rule will be required to comply with specific emission standards;
• Products manufactured with ultra-low formaldehyde or no-added formaldehyde (NAF) resins will be exempt with proper recordkeeping practices; and
• Regulated products must comply with emission standards, as determined by a third-party certifier, in order for a product to be labeled as TSCA Title VI compliant.
While most provisions will become effective within one year of rule publication, laminated products fabricated with wood or woody-grass veneer attached to MDF or PB will be subject to the same certification and testing requirements as hardwood plywood seven years after rule publication.
The exposure model used by the U.S. EPA is called the Formaldehyde Indoor Air Model – Pressed Wood Products (FIAM-pwp). The model has been peer-reviewed, and is publically available. The model uses emissions test data similar to the data that will be required under the U.S. EPA emissions standard. It estimates the concentration of formaldehyde released from one or more composite wood products, and the subsequent human inhalation exposure. The model considers important determinants of exposure like indoor temperature, age of source materials, and the amount of time spent indoors. As is true with any model, there are some limitations in the modeling approach used by U.S. EPA. One important thing to know about formaldehyde is that porous materials such as drywall and furnishings can absorb and retain formaldehyde. U.S. EPA's model does not account for this phenomenon, so it is possible that in some environments, short-term peak formaldehyde exposure could be lower than predicted.
EPA used FIAM-pwp to evaluate scenarios of airborne formaldehyde concentrations in homes, daycares, schools, workplaces, vehicles, and the outdoors for various types of structure types in the different climatic zone. In total, U.S. EPA evaluated several thousand exposure scenarios during the preparation of the standard. In the final standard, U.S. EPA focused on a comparison of a standard consistent with the CARB ATCM to several alternative emission standards for laminate flooring. Taking into account the cost-benefit analysis, the agency elected to include laminate flooring in the definition of hardwood plywood, with exemptions for certain types of resins. The FIAM-pwp model, and other computational modeling techniques, can be used to prospectively and retrospectively estimate formaldehyde emissions from composite wood products subject to the new U.S. EPA emission standard. These topics, and more, will be discussed in more detail in future blogs in this series.
How Cardno ChemRisk Can Assist with Questions about Formaldehyde
As a state-of-the-art scientific consulting firm, Cardno ChemRisk is well respected for its leadership in human health risk assessment – including computational modeling and statistical services. Cardno ChemRisk has extensive experience using computational modeling to understand past and future exposures in both occupational and environmental settings, especially in situations where collecting measurements is either impossible or impractical. In addition, Cardno ChemRisk applies a variety of statistical methods to understand the important relationships hidden within an environmental or occupational data set. If you are interested in discussing our recommendations for consumer product formaldehyde exposure modeling in more detail, please contact the Ken Unice, Science Advisor, and Computational Science Service Area Lead at Cardno ChemRisk.