Sodium perchlorate

Endpoint summary

Additional information

Stability:

Sodium perchlorate is highly soluble, stable and is a non complexing agent. This lack of reactivity results from the high strength of the chlorine-oxygen bonds, and the requirement that reduction proceed by removal of an oxygen atom, rather than by direct interaction of a reducing agent with the chlorine atom.

Biodegradation:

According to REACH, no data is required for characterizing readily biodegradation portential of an inorganic substance. Nevertheless few references are available allowing a better characterization of perchlorate behaviour in environment (especially sediment and soil for which data are available). Perchlorate's low reactivity at ambient temperatures and dilute concentrations might imply that direct chemical transformation of perchlorate in the environment-through participation in oxidation-reduction reactions without the influence of microorganisms is unlikely. However, a growing number of field and laboratory studies have shown that perchlorate can be biologically transformed. Bacteria capable of perchlorate degradation are widely distributed in nature and significant numbers of perchlorate reducing bacteria have been found in samples collected from both pristine and contaminated environments.

Bioaccumulation:

Sodium perchlorate is not bioaccumulative as demonstrated in the frame of experiments equivalent to OECD 305. Therefore secondary poisoning is not foreseen as a possible issue. Terrestrial data are not required according to REACH but based on the available data about aquatic compartment and also intrinsic perchlorate properties it can be safely concluded that perchlorate is not bioaccumulative for terrestrail organisms.

Transport and distribution:

Once released to the environment, the physical, chemical and biological processes that affect the fate and transport of perchlorate include dissolution of source material (in the case of solids), advection, dispersion and diffusion, sorption, and biological degradation. When dissolved in soil pore water, groundwater and surface water, perchlorate's limited ability to sorb to mineral surfaces results in migration dominated by the bulk movement of water (advection) and mixing processes (dispersion). In cases where the advective velocity of the migrating water in low, such as within a clay layer in an aquifer, diffusion processes may become important.

As a conclusion, that means that this substance is highly mobile in the environment once dissolved in water and does not typically sorb to soils or sediment particles.

Perchlorate salts have very low vapor pressure and therefore solid compounds are not expected to volatilize under ambient conditions. In addition, dissolved perchlorate anions do not tend to partition from the aqueous to the gas phase. Thus perchlorate cannot readily volatilize from water under ambient conditions (From Sellers et al, 2006).

Very high concentrations of perchlorate (percent levels) are rare in the general terrestrial environment, occuring primarily at manufacturing facilities or at sites that tested or burned formulations or explosives containing high concentrations of hte oxidizer. Soil at other locations may contain trace levels (µg/kg) of perchlorate. The best example at the local level would be areas that were routinely used as an ignition platform for fireworks displays. Perchlorate is also used as an oxidizer in roadside flares, so very limited soil exposure may occur in areas where flares are used (or ditches that may have recived stormwater runoff from these areas).

Although a careful review of the literature shows a few sites where the maximum value of perchlorate in soil exceeds 1500 mg/kg, it may be misleading to focus on the highest detected conecntrations because soil contamination at many sites tends to spatially distribute in clusters or hot-spots, for instance those located in and around targets used at military ranges. The frequency distribution of perchlorate concentrations, like most chemicals in soil at hazardous waste sites is therefore log normal and heavily skewed to the left, meaning the majority of soil analyses would be observed below the detection limit. As a consequence, most terrestrial animals inhabiting a site, due to the selective nature of foraging activity are anticipated to be exposed to, on average, lower soil levels than the maximum values which are measured.

Case study: Massachusetts Military Reservation (MMR), Cape Cod, Massachusetts

Less than 10% of the soil samples (216 out of 2500) at MMR contained detectable perchlorate (range was 0.0012 to 27 mg/kg, with a median and mean concentration of 0.0021 and 0.252 mg/kg, respectively). A careful review of the literature shows that most of soil samples at hazardous waste sites (that have a known history of exposure to perchlorate) are less than 20 mg/kg.

Alsop et al. (Assessing alternate approaches to estimating uptake of compounds by plants and animals in ecological risk assessments, The 19th annuam international conference on soils, sediments and water, University of Massachusetts, Amherst, October 20 -23, 2003) studied perchlorate uptake by plants and small mammals in one area at MMR. Soil in the study area contained perchlorate concentrations that ranged from non-detect to a maximum concentration of 27 µg/kg. They reported that perchlorate was taken up by plants and the perchlorate concentrations ranged between non-detect to 140 µg/kg. Perchlorate was not detected in earthworms exposed to perchlorate containing soil. Perchlorate was not detected in mice or voles collected from the study area but it was detected in a single shrew sample at 140 µg/kg.