Risk assessment


What is a risk assessment?

A risk assessment evaluates whether emissions of a chemical substance, occurring at each stage of its life-cycle (production, formulation, processing, use and disposal), affect human health or the environment. Risk evaluations are usually performed at local and regional levels, as well as at a continental scale.

Protection goals

  • Environment: atmosphere, aquatic organisms, sediment- and soil-dwelling organisms, micro-organisms in waste water treatment plants, mammals and birds exposed via accumulation up the food chain.
  • Humans: workers exposed at the workplace, consumers exposed via consumer products, humans indirectly exposed via air, food, and drinking water.
EU risk assessment of Antimony Trioxide

The risk assessment (RA) of Antimony Trioxide was an obligatory risk assessment as prescribed by the EU Existing Substances Regulation (EEC n° 793/93). It was finalised in May 2008 (summary of the outcome [PDF - 158 KB]).

More information on the EU Risk Assessment principles can be found on the website of the European Chemicals Bureau.

After the EU approval of the Risk Assessment (RA) on Antimony Trioxide, the members of the OECD also accepted the report under the SIAP program at their meeting on October 14th 2008. The approval of the SIAP means in practice that all OECD member states (including those who signed the Mutual Acceptance of Data agreement such as South Africa, Brazil, Indonesia and soon China) agree to use this document to set environmental and human health standards or to assess antimony trioxide. The SIAP has been made publicly available.

Human health

During the review process of the EU risk assessment, i2a filled a lot of data gaps with regard to the effects of Antimony Trioxide (ATO) to human health. Studies were commissioned to investigate acute toxicity (sensitisation, irritation and inhalation toxicity), toxicokinetics, mutagenicity and developmental toxicity. i2a also made a great effort to gather human exposure data from producers and downstream users of ATO.

Using both existing and new research data, the following conclusions were drawn in the risk assessment:

  • Workers: concerns were identified only for (a) pulmonary toxicity, which requires risk reduction measures, and (b) skin irritation (under conditions of perspiration), which indicates the need for classification.
  • Consumers: no concerns were identified after evaluating the following important exposure scenarios: drinking from PET bottles; contact with fabrics; sucking on toys; inhalation of indoor air.
  • Man exposed indirectly via the environment: no concerns were identified after evaluating exposure via: the food, mother's milk, drinking water and outdoor air.
For workers' exposure, risk reduction measures are included in the EU REACH regulation. These measures ensure safe use at the workplace.

More information with regard to the human health effects of ATO:

  • ATO is not a sensitizer nor an eye or respiratory tract irritant,
  • ATO is irritating to human skin for workers under conditions of heat and severe perspiration (but does NOT require classification for it),
  • Acutely, ATO is not harmful via ingestion (LD50 > 20 g/kg body weight), nor via inhalation (4-h LC50 > 5 mg/L air) or dermal (LD50>8300 mg/kg) exposure,
  • For repeated (long-term) oral exposure, the NOAEL (no observed adverse effect level, i.e. the highest tested exposure level not giving a significant adverse effect) is 1686 mg/kg/d,
  • For repeated (long-term) exposure via inhalation, the NOAEC (no observed adverse effect concentration, i.e. the highest tested exposure concentration not giving a significant adverse effect) is 0.51 mg/m3, based on impaired lung clearance. This NOAEC was determined in a study with a high background incidence of lung inflammation in controls (Newton et al. (1994)). Therefore, there is some uncertainty regarding the reliability of the numerical value.
  • ATO is not toxic to male or female reproductive tissues and no evidence of developmental toxicity was observed.
  • There is no concern for genotoxicity (i.e. chromosomal aberrations or DNA damage) at biological relevant concentration levels,
  • ATO is classified as carcinogen category 2 according to CLP regulation EC n° 1272/2008 (‘suspected of causing cancer via inhalation’), denoting that ATO causing concern, but scientific data available are inadequate. It is accepted that ATO is a threshold carcinogen, meaning that cancer may only result from long-term accumulation of ATO particles in the lungs, causing inflammation reactions which may later lead to fibrosis, and possibly tumour formation. Since the available studies investigating the adverse effects of long-term exposure via inhalation all have serious drawbacks hampering the evaluation of the adverse effects of ATO on the lungs, the US NTP (US National Toxicology Program) has nominated ATO for further research. At the end of 2007, a 14 d range-finder on rats and mice was conducted by the US NTP, and the conclusions are available on the NTP website. A subchronic and chronic toxicity study with both rats and mice has been performed as well (finalized in 2010), but results have not yet been published on the NTP website.
Please note that the observation of adverse effects (= ‘hazard identification’) does not automatically imply that there is a risk: only when the calculated or measured exposure level/concentration exceeds the critical hazard concentration, a risk is identified.

Classification & labelling (CLP Regulation (EC) n° 1272/2008)

  • Warning (GHS08)
  • Carcinogen cat 2 (H351 – suspected of causing cancer via inhalation)
  • P202: Do not handle until all safety precautions have been read and understood.
  • P281: Use personal protective equipment as required.
  • P308+P313: IF exposed or concerned: Get medical advice/attention.
  • P405: Store locked up.

For the environmental part of the EU risk assessment of antimony trioxide (ATO), i2a filled several data gaps (e.g. toxicity to soil and sediment organisms). Together with the human exposure data, i2a collected environmental exposure data from producers and downstream user of ATO.

Using the new information provided by i2a as well as carefully evaluated existing data, the following conclusions were drawn in the risk assessment

  • (I) Freshwater organisms – no risk identified
  • (II) Freshwater sediment organisms – no risk identified, except for one production site and for textile back coating companies that did not provide environmental emission data
  • (III) Microorganisms in waste water treatment plants – no risk identified
  • (IV) Soil organisms – no risk identified
  • (V) Atmosphere – no risk identified
  • (VI) Secondary poisoning (i.e. adverse effects due to accumulation up the food chain) – no risk identified
  • (VII) Marine environment – currently there is no need for concern

Measured and/or worst-case modeled antimony release data/estimates show that none of the identified uses of ATO pose a risk to the environment at continental, regional and local scale. As such, no further risk reduction measures  need to be proposed in the ATO REACH  registration dossier.

Overview of PNECs derived in the EU risk assessment:

Note: a PNEC (predicted no effect concentration) is derived based on the results of reliable ecotoxicity studies and represents the concentration that should not be exceeded to avoid adverse effects.

  • PNECsurface water = 113 µg Sb/L
  • PNECsediment = 11.2 mg Sb/kg(dry weight) (or 7.8 mg Sb/kg(wet weight))
  • PNECmicroorganisms = 2.55 mg Sb/L
  • PNECsoil = 37 mg Sb/kg(dry weight)
  • PNECmarine water = 11.3 µg Sb/L
  • PNECmarine sediment = 2.24 mg Sb/kg(dry weight) (or 1.6 mg Sb/kg(wet weight))
  • PNECsecondary poisoning = 374.8 mg/kg food

Please note that the observation of adverse effects does not necessarily mean that there is a risk. To evaluate whether or not there is a risk, PNECs should be compared to calculated or measured exposure concentrations. The outcomes of the risk characterisation performed in the EU risk assessment report are mentioned above.

Classification & labelling:

  • ATO is not classified as dangerous for the environment.


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