ProScale is a tool in the Mistra SafeChem (MSC) toolbox, providing a hazard and exposure based scoring system for comparing chemical risks associated with products in a life cycle perspective. Current scope of ProScale cover human toxicity via direct exposure, e.g., worker exposure during production. Together with BASF, an industry partner within the programme, a case study for testing ProScale was developed. The aim of the case study was to perform a ProScale assessment of the human toxicity potential of the life cycle of two flame retardant polyamides.
The goal of the case study was to compare the cradle-to-gate ProScale score (PSP) (inhalation and dermal exposure) of the two flame retardant polyamides.The first polyamide, herein referred to as Product A, is based on a brominated flame retardant and represents the reference product. The second, Product B, is a nitrogen-based flame retardant free from halogens. In this assessment the product systems are represented as branches of interconnected unit-processes, i.e., production steps from raw material outtake (cradle), coming together in a final product output (gate).The results indicate that Product B has a lower toxicity potential than Product A, as the PSP per kg of product, inhalation and dermal, was 220 and 20 for Product A and 450 and 40 for Product be, respectively. Figure 1. Visualization of the ProScale scores for the cradle-to-gate systems (PSP) of Product A and B.
Approximately 40% of the PSP from Product A came from the polyamide and its upstream processes. The contribution from this branch was the same in both systems, i.e., it was not this branch that caused the difference in the PSPs shown in Figure 1. Instead, 60% of the PSP from Product A came from the flame retardant, and mainly its upstream processes. Almost 100% of the PSP from the flame-retardant branch in Product A came from crude oil extraction and refining. Once crude oil is extracted it undergoes refining in which 20kg crude oil is required to produce 1kg of naphtha. Crude oil is classified as H350, placing the substance in the highest hazard class. The high mass flow contribution and the hazard class gave the oil refining a high ProScale score for the unit process (PSU), resulting in a major contributing to the total PSP.
Product B is also produced from substances that originates from naphtha from oil refining. However, as the downstream mass flows were lower, the contribution from the oil refining to the final PSP of Product B system was lower.It was concluded that i) Product B is indicated to have a lower toxicity potential compared to Product A (the reference) with regards to human toxicity via direct exposure in the defined cradle-to-gate systems, and ii) The use of raw materials originating from crude oil can have a high impact on the PSP in downstream processes even though the value chain is rather long. This is important to keep in mind when defining the system boundaries for a ProScale assessment.
Göteborg: IVL Svenska Miljöinstitutet, 2024.