Toxicological and ecotoxicological properties of gas-to-liquid (GTL) products. 2. Ecotoxicology

Abstract

Gas-to-liquid (GTL) products are synthetic hydrocarbons produced from natural gas using a catalytic process known as the Fischer-Tropsch process. This process yields a synthetic crude oil that consists of saturated hydrocarbons which can subsequently be refined to a range of products analogous to those obtained from petroleum refining. However, in contrast to their petroleum-derived analogs, GTL products are essentially free of unsaturated or aromatic compounds and do not contain any sulfur-, oxygen-, or nitrogen-containing compounds. Under new chemical substance notification requirements, an extensive testing program covering the entire portfolio of GTL products has been undertaken to assess their hazardous properties to human health and environment. The results of these studies have been summarized in a two-part review. Part 1 provides an overview of the mammalian toxicity hazardous properties of the various GTL products. This second part of the review focuses on the aquatic, sediment, terrestrial, and avian toxicity studies which assess the ecotoxicological hazard profile of the GTL products. Many challenges were encountered during these tests relating to dosing, analysis and interpretation of results. These are discussed with the intent to share experiences to help inform and shape future regulatory mandates for testing of poorly soluble complex substances. As was the case with the mammalian toxicology review, there were a few cases where adverse effects were found, but overall the GTL products were found to exert minimal adverse ecotoxicological effects and these were less severe than effects observed with their conventional, petroleum-derived analogs.

Terrestrial Toxicity of Synthetic Gas‐to‐Liquid versus Crude Oil–Derived Drilling Fluids in Soil

“…It was concluded that GTL 11–24 would be a better alternative for the environment than LTMO and possibly other petroleum‐derived oils, especially with freshly spiked soils. This is consistent with the previously published ecotoxicological information on GTL products (Whale et al 2018).…”

“…With a GTL NABF, soybean and tomato had an EC50 > 10 000 mg/kg, mustard had an EC50 of 4300 mg/kg, and oat and perennial ryegrass had an EC50 of 6200 mg/kg. Overall, GTL NABFs did not elicit strong toxicological responses in any of the standardized studies performed previously (Whale et al 2018).…”

“…With a GTL NABF, soybean and tomato had an EC50 > 10 000 mg/kg, mustard had an EC50 of 4300 mg/kg, and oat and perennial ryegrass had an EC50 of 6200 mg/kg. Overall, GTL NABFs did not elicit strong toxicological responses in any of the standardized studies performed previously (Whale et al 2018). The present study examined 2 different GTL NABF products and their relative terrestrial toxicity in comparison with petroleum-derived NABF products.…”

“…In standardized toxicological testing, GTL products have been shown to exert less severe effects than their petroleum‐derived equivalents, consistent with our results. Terrestrial toxicity tests of related GTL products showed no toxicity in chronic and acute tests with earthworms ( E. fetida ), and an earthworm reproduction test on a GTL NABF with a very similar carbon range had a 56‐d median effect concentration (EC50) of 4160 mg/kg dry soil (Whale et al 2018). Seedling emergence tests with soybean ( Glycine max ), tomato ( Lycopersicon esculentum ), mustard ( Sinapis alba ), and oats ( Avena sativa) showed EC50 >1000 mg/kg dry soil for related GTL products; however, the perennial ryegrass ( Lolium perenne ) had a 560 mg/kg no‐observable‐effect concentration for growth.…”

Use of new approach methodologies to study the developmental toxicity of polycyclic aromatic hydrocarbons

“…or contain very low concentration of PACs, such as low-boiling petroleum substances, bitumen and oxidized asphalt and also all gas-to-liquid products (synthetic analogues of petroleum substances without aromatic compounds), no developmental effects were observed in rats (Boogaard et al, 2021;Whale et al, 2018). successfully correlated the developmental toxicity and the 3-to 7-ring PAC content of the petroleum substances.…”