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Description of key information

There are no experimental studies available in which the toxicokinetic behavior of 1,3-propanesultone (CAS 1120-71-4) has been assessed.

In accordance with Annex VIII, Column 1, Item 8.8.1, of Regulation (EC) 1907/2006 and with Guidance on information requirements and chemical safety assessment Chapter R.7c: Endpoint specific guidance (ECHA, 2014), assessment of the toxicokinetic behavior of the substance is conducted to the extent that can be derived from the relevant available information. This comprises a qualitative assessment of the available substance specific data on physico-chemical and toxicological properties according to the relevant Guidance (ECHA, 2014).

1,3-propanesultone undergoes rapid hydrolysis leading to release of hydroxypropanesulfonic acid which dissociates in aqueous environment. Oral and dermal absorption is likely both for 1,3-propanesultone and the dissociated form of the hydrolysis product hydroxypropanesulfonic acid. Absorption via inhalation is assumed to be as high as via the oral route of exposure. Hydroxypropanesulfonic acid in its dissociated form will be distributed in the body and excretion is expected mainly via urine.

Key value for chemical safety assessment

Bioaccumulation potential:
no bioaccumulation potential

Additional information

Basic toxicokinetics

There are no experimental studies available in which the toxicokinetic behavior of 1,3-propanesultone (CAS 1120-71-4) has been assessed.

In accordance with Annex VIII, Column 1, Item 8.8.1, of Regulation (EC) 1907/2006 and with Guidance on information requirements and chemical safety assessment Chapter R.7c: Endpoint specific guidance (ECHA, 2014), assessment of the toxicokinetic behavior of the substance is conducted to the extent that can be derived from the relevant available information. This comprises a qualitative assessment of the available substance specific data on physico-chemical and toxicological properties according to the relevant Guidance (ECHA, 2014).

1,3-propanesultone is a colorless powder at 20°C and 1013.25 hPa. The determination of water solubility is not applicable as the substance is hydrolytically unstable at pH4, 7 and 9 (half-life less than 12 h). Due to the decomposition of the substance also the determination of a log Pow is not possible. A vapor pressure of 0.0027 hPa at 20°C was determined.

1,3-propanesultone is a highly reactive alkylating agent. Its carcinogenic potency has been demonstrated in several studies with rats and mice. The substance induces a high incidence of local tumors and, to a lesser extent, systemic tumors as well. In numerous short-term tests, 1,3-propanesultone has been shown to be a direct mutagen.

The potential of a substance to be absorbed in the (GI) tract may be influenced by chemical changes taking place in GI fluids as a result of metabolism by GI flora, by enzymes released into the GI tract or by hydrolysis. These changes will alter the physico-chemical characteristics of the substance and hence predictions based upon the physico-chemical characteristics of the parent substance may no longer apply (ECHA, 2014).

The molecular weight of 1,3-propanesultone (122 g/mol) is lower than 500 g/mol, indicating that absorption of the substance is likely (ECHA, 2014). However, due to the unstable properties of 1,3-propanesultone and hydrolisation to hydroxypropanesulfonic acid absorption of 1,3-propanesultone in higher amounts is not expected. Hydroxypropanesulfonic acid will dissociate and could therefore be absorbed.

The available acute oral toxicity key study on 1,3-propanesultone showed a LD50 value between 100 – 200 mg/kg bw in rats (OTS, 1992). Signs of toxicity were characterized by the observation that the animals were moderately to very weak and showed prostration, salivation, dark eyes, tremor, gasping, diarrhea and convulsions. Oral carcinogenicity studies in rats showed various types of malignant tumors, primarily tumors of the brain with a possibility of induction of leukemia and carcinomas of the small intestine (Weisburger, 1981) and tumor in the nervous system, subcutaneous and nephroblastoma (Druckrey, 1970).

Acute oral toxicity data with the hydrolysis product 3-hydroxypropanesulfonic acid revealed a LD50 value of > 2000 mg/kg bw. One female was found dead 30 minutes after dosing. Clinical signs of toxicity noted in one male during Days 4 to 13 included distended abdomen, dehydration, emaciation, hunched posture, decreased respiratory rate, gasping, laboured and noisy respiration and tiptoe gait. Surviving animals showed an expected gain in bodyweight during the study except for one male which showed bodyweight loss during the first week and expected gain during the second week of the study. Abnormalities noted at necropsy of the female that died during the study were abnormally red lungs, dark liver, dark kidneys, severe haemorrhage of the gastric mucosa and severe haemorrhage of the small and large intestines.

In conclusion, based on the available data and physico-chemical properties, oral absorption is likely both for 1,3-propanesultone and the dissociated form of its hydrolysis product.

The dermal uptake of liquids and substances in solution is higher than that of dry particulates, since dry particulates need to dissolve into the surface moisture of the skin before uptake can begin. Molecular weights below 100 favour dermal uptake, while for those above 500 the molecule may be too large (ECHA, 2014).

The molecular weight of 1,3-propanesultone (122 g/mol) is lower than 500 g/mol, indicating that absorption of the substance is likely (ECHA, 2014). However, it is a solid and needs to dissolve into the surface moisture. QSAR estimation resulted in a dermal absorption of 0.0544 mg/(cm2*h).

Moreover, it has to be considered that damage to the skin surface may enhance penetration if the substance is a skin irritant or corrosive, (ECHA, 2014). The experimental animal and human data show that 1,3-propanesultone has skin corrosive potential, which could lead to enhanced penetration of the substance due to local skin damage (OTS, 1992).

The available acute dermal toxicity data on 1,3-propanesultone showed a LD50 value of 660 mg/kg bw for rabbits (MAK, 1985) and between 700 – 1400 mg/kg bw for the guinea pig (OTS, 1992). Doak et al. (1976) investigated the carcinogenic activity of 1,3-propanesultone by skin painting. The incidence of local and systemic tumors was much higher after chronic treatment than after single or short term treatment. Systemic tumors mainly consisting of lymphoma sarcomas and reticulosarcoma of the spleen, hepatomas, and lung tumors. Myeloid hyperplasia was also noted. In addition, epidermal papillomas were observed.

Overall, based on the available information, dermal absorption of 1,3-propanesultone and the dissociated form of its hydrolysis product is likely.

1,3-propanesultone has a vapor pressure of 0.0027 hPa at 20°C. Hence, the potential for exposure and subsequent absorption via inhalation during normal use and handling cannot be excluded. As already described for oral absorption, 1,3-propanesultone hydrolysis to hydroxypropanesulfonic acid which dissociates and could therefore be absorbed.

After acute inhalation exposure to the test item for 6 h, a LC50 (6 h) of approximately 1.7 mg/L air was derived (OTS, 1992). Absorption via inhalation is therefore assumed to be as high as via the oral route in a worst case approach.

Distribution of a compound within the body depends on the physico-chemical properties of the substance; especially the molecular weight, the lipophilic character and the water solubility. In general, the smaller the molecule, the wider is the distribution. If the molecule is lipophilic, it is likely to distribute into cells and the intracellular concentration may be higher than extracellular concentration, particularly in fatty tissues (ECHA, 2014).

1,3-propanesultone undergoes rapid hydrolysis leading to release of hydroxypropanesulfonic acid which dissociates in aqueous environment and could therefore be absorbed and distributed in the body. Experimental data obtained in carcinogenicity studies showed abnormalities in spleen, thymus and lymph nodes and several local and systemic tumors showing that the dissociated hydrolysis product may at least reach the visceral organs.

Characteristics favourable for urinary excretion are low molecular weight (below 300 in the rat), good water solubility, and ionization of the molecule at the pH of urine. As 1,3-propanesultone will rapidly be hydrolysed in the gastro-intestinal fluids, the dissociated form of the hydrolysis product hydroxypropanesulfonic acid is more important for consideration. Due to the low molecular weight of both substances and ionization of the hydrolysis product it is expected that excretion is mainly via urine.