Gas Import Jetty & Pipeline Discussion

Odorisation process

Odorisation process


Re: Odorisation process

APA Employee

Hi KerryRainer,


We’ve spoken to our specialists regarding your unresolved query:


The main chemical ingredients in Spotleak 1005 are tetrahydrothiophene and 2-methyl-2-propanethiol. Both of these chemicals are volatile and do not persist for long periods in the environment or accumulate in living organisms. The main hazards associated with these chemicals are offensive odour and flammability. APA has strict handling and transport procedures in place to prevent leaks and measures for managing the odour and fire hazards in the rare event that a spill were to occur. These procedures would also be protective of health effects in the unlikely event of a spill or leak.


Our specialists have provided additional technical information to address your question regarding the effect of a spill on odorant chemicals on soil and water.


Tetrahydrothiophene (also known as thiophane or THT) is not soluble in water and if released to the environment in a spill it will remain as a separate phase with little tendency to sorb to soil. It is a volatile organic compound which would be expected to be present as a gas in association with a spill of the liquid. In the atmosphere it would be expected to rapidly break down due to oxidation by hydroxyl radicals in the atmosphere. It may be degraded biologically in the environment and due to its low boiling point and low octanol water partition coefficient it is not expected to bioconcentrate in living organisms. Human toxicity data are limited to a study of workers at a factory producing THT, which identified effects from a short (unspecified) exposure were headache, palpitations, giddiness, nausea or a general feeling of being unwell. Animal studies have identified skin or inhalation tract irritant effects but not carcinogenicity/mutagenicity. THT is highly flammable and intensely odorous. It has an odour threshold of 1 ppb. A human health toxicity reference value has not been published in Australia, but a search of international sources identified that the Netherlands has established a tolerable concentration in air of 180 ppb. This means that a human would detect the odour from THT at a level in air that was more than two orders of magnitude lower than the level at which no health effects would be expected for long term exposure.


2 methyl 2 propanethiol (also known as tert-Butyl mercaptan or TBM) is a volatile organic compound which if released to the environment will exist mainly as a gas. In the ambient atmosphere, TBM will be rapidly degraded by reaction with hydroxyl radicals. If released to soil, TBM is expected to volatilise and unlikely to sorb to soil. If released into water, it is only slightly soluble in water and is expected to volatilise and not to sorb to sediment. The potential for bioconcentration in aquatic organisms is low. If a spill occurs, human exposure to TBM could occur primarily through inhalation. Studies of human exposure to TBM have identified that it is irritating to the eyes and the respiratory tract. Exposure at high levels may result in lowering of consciousness. The strong, offensive smell of mercaptans can cause cough, dizziness, headache and nausea. Based on human and animal studies TBM is not expected to be carcinogenic/mutagenic. TBM has a strong offensive odour, with an odour threshold of <0.33 ppb. Safe Work Australia has set a time weighted average (TWA) for occupational exposure to butyl mercaptan of 500 ppb, but other toxicity reference values could not be identified in Australia or internationally. Nevertheless considering the TWA is more than two orders of magnitude greater than the odour threshold, it is considered that TBM would be detected by smell at concentrations well below those that may result in a long term health effect.


Therefore, if a spill of Spotleak 1005 were to occur, the offensive odour and flammability hazards would be the primary concerns for emergency response and based on the available information on human or environmental toxicity, clean up to reduce exposure to levels below the odour threshold would also protect human health.


We hope the information provided better answers your questions.

Madeline, Community Engagement Advisor, APA Group