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MTDID 22327 is volatile (vapor pressure, 213 mm Hg at 20 °C) and of low water solubility (range for predominant constituents, 0.679 μg/L to 758 µg/L at ca. 23 - 24 °C).  A range of Henry's Law constants (expressed as the ratio of vapor phase partial pressure of constituent over aqueous phase concentration) of 171 - 4020 atm∙m³/mol, at 22 °C was established by read-across from category members.  A range of log Kow values of 4.3 - 6.14 at 23 °C was similarly established by read-across from predominant constituents.  However, it is not expected that MTDID 22327 will have a significant presence in the aquatic compartment, and bioaccumulation in aquatic organisms is not expected.

MTDID 22327 is not expected to partition from the atmosphere to moist soils or surface waters.  MTDID 22327 is manufactured for export; it is not expected to be released to aquatic systems or soils.  Upon direct release of MTDID 22327 to the aquatic compartment, the chemical would be expected to volatilize rapidly.  However, as noted MTDID 22327 release is entirely to the atmosphere.  MTDID 22327 is not expected to partition to aquatic compartments from the atmosphere, therefore no exposure to aquatic organisms is expected.

Bioaccumulation studies are not required at this annual volume, and no studies were done on bioaccumulation of MTDID 22327.  Based on the log Kow range of 4.3 – 6.14, some constituents of this substance would be considered bioaccumulative in aquatic organisms; the predominant constituent with its log Kow of 4.3 would not.  However, substantial bioaccumulation of MTDID 22327 in aquatic organisms is not expected due to lack of exposure in aquatic systems.  MTDID 22327 is expected to reside entirely in the atmospheric compartment, so air breathing organisms were evaluated for bioaccumulation potential.  According to Chapter R.7.10.3.4 of the Technical Guidance (Other indication of bioaccumulation potential):

"For air-breathing organisms, respiratory elimination occurs via lipid-air exchange, and such exchange declines as the octanol-air partition coefficient (Koa) increases, with biomagnification predicted to occur in many mammals at a log Koa above 5. Such biomagnification does not occur if the substance and its metabolites are rapidly eliminated in urine (i.e. have a log Kow of around 2 or less). Thus the bioaccumulation potential in air-breathing organisms is a function of both log Kow and log Koa. In contrast, respiratory elimination in non-mammalian aquatic organisms occurs via gill ventilation to water, and this process is known to be inversely related to the log Kow (hence an increase in log Kow results in a decrease in the rate of elimination and hence increase in the accumulation potential)."

Log octanol-air partition coefficient (log Koa) values ranging from 0.39 to 1.52 were calculated for MTDID 22327 using the relationship:

Koa (unitless) = Kow / Kaw

Where Kow is octanol:water partition coefficient and Kaw is the dimensionless Henry’s Law constant.  Input data were derived from category members. As per Kelly and Gobas (1), chemicals with log Koa < 4 do not biomagnify regardless of the Kow  because of efficient elimination via air exhalation (or, in this case, extremely inefficient absorption via air inhalation).  According to the classification scheme proposed in Chapter R7.10.3.4, MTDID 22327 is a non-polar volatile (high log Kow and low log Koa), and is not expected to bioaccumulate in air-breathing organisms.  As stated, the potential to accumulate in aquatic organisms is mitigated by the lack of relevance of the aquatic exposure pathway. Therefore, bioaccumulation of MTDID 22327 in terrestrial or aquatic organisms is not expected.

Reference:

1) Kelly, B.C. and F.A.P.C. Gobas.  2003.  An Arctic Terrestrial Food-Chain Bioaccumulation Model for Persistent Organic Pollutants.  Environ. Sci. Technol Vol. 37, No. 13, pp 2966–2974.