Halophosphate

Endpoint summary

Description of key information

Using a theoretical approach and the available physico-chemical properties and toxicological data, the following absorption factors were derived for risk assessment purposes: oral absorption factor: 10%; dermal absorption factor: 10%; inhalation absorption factor: 100%

Key value for chemical safety assessment

Absorption rate - oral (%):

10

Absorption rate - dermal (%):

10

Absorption rate - inhalation (%):

100

Additional information

Halophosphate is considered to be insoluble in water. In general a substance needs to be dissolved before it can be taken up from the gastro-intestinal tract. Thus, the water insolubility can be considered a potentially rate-limiting factor for the absorption of the compound. In addition, also the molecular weight of this substance is not favourable for absorption. After oral administration, it is unlikely that Halophosphate will show a high systemic exposure. In the presence of food and bile salts some systemic exposure might be possible. For risk assessment purposes the oral absorption of Halophosphate is set at 10% as a worst case assumption.

 

Once absorbed, distribution of Halophosphate throughout the body will be limited due to its water insolubility.

 

Based on the particle size distribution study performed with Halophosphate, particles < 100 μm which have a potential to be inhaled, are present. Particles with an aerodynamic diameter below 50 μm may reach the thoracic regions, whereas particles with an aerodynamic diameter below 15 μm may reach the alveolar region of the respiratory tract. The water insolubility of Halophosphate indicates that Halophosphate will not dissolve into the mucus lining of the respiratory tract and the deposits in the nasopharyngeal region will likely to be coughed or sneezed out of the body, or swallowed. As most of the particles have a size < 10 μm (68.16%), the fraction that will reach the alveolar region of the respiratory tract will be available for absorption. For risk assessment purposes the inhalation absorption of Halophosphate is set at 100%.

 

Halophosphate being a solid which is considered to be insoluble in water has no real potential for dermal absorption. Its molecular weight above 500 does not favour dermal absorption. Based on these physical/chemical properties of Halophosphate, dermal absorption is considered to be low. Although the criteria for 10% dermal absorption as given in the REACH guidance (Guidance for the implementation of REACH. Guidance on information requirements and chemical safety assessment. Chapter R.7c: Endpoint specific guidance. European Chemical Agency, May 2008) (MW > 500 and log Pow < -1 or > 4) are not met as data on log Pow are not available for inorganic substances, 100% dermal absorption is considered not relevant for Halophosphate as it is generally accepted that dermal absorption does not exceed oral absorption. For risk assessment purposes therefore, 10% dermal absorption of Halophosphate as default value is considered to be appropriate.

 

Based on the present available data, no additional conclusions can be drawn on the distribution, metabolism and excretion of Halophosphate after dermal and inhalatory absorption.