Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:10:p3
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 10 (pt 3/11)
Character Range: 2242227–2245097

10.3.2     Dermal absorption
Review of dermal absorption by MfE (2011) has noted that 'Mercury reacts with skin proteins, and as a result penetration does not increase commensurably with increasing exposure concentration but rather approaches a plateau value. Mercury has a permeability coefficient in the order of 10–5 cm/h (Guy et al. 1999), which compares to permeability coefficients in the order of 10–4 cm/h for lead.' As dermal absorption for lead has not been considered to be negligible, the potential for dermal absorption of mercury has been considered.

ATSDR (1999) notes that absorption of mercurous salts in animals can occur through the skin, though no quantitative data is available, hence a default value of 0.1% has been adopted based on the lower end of the range for metals presented by US EPA (1995).

ATSDR (1999) also noted no information was identified for absorption of methylmercury via dermal absorption. The Environment Agency (EA 2009) notes that dermal absorption of methyl mercury is reported to be similar to that of inorganic mercury. Hence the value adopted for inorganic mercury has also been adopted for methyl mercury. It is noted that dermal absorption of dimethylmercury has been reported to be of potential significance and may need to be considered in a site-specific assessment if identified as the key form of mercury in soil.

US EPA (2004) has recommended the use of a gastrointestinal absorption factor (GAF) of 7% for inorganic mercury based on mercuric chloride and other soluble mercury salt studies used in the derivation of the oral RfD. The GAF is used to modify the oral toxicity reference value to a dermal value in accordance with the US EPA (2004) guidance provided.

    10.3.3     Inhalation of Dust
Inorganic mercury and methyl mercury are not volatile and inhalation exposures associated with particulates outdoors and indoors are expected to be of less significance than ingestion of soil. While likely to be negligible, potential inhalation exposures associated with dust have been considered in the HIL derived. Note that if elemental mercury is present then vapour phase issues need to be considered on a site-specific basis.

    10.3.4     Plant Uptake
A detailed review of the plant uptake of mercury (primarily elemental and inorganic mercury) is presented in EA (2009). This review considered studies that are based on the uptake of mercury into green vegetables, root vegetables, tuber vegetables, herbaceous fruit, shrub fruit and tree fruit. The review provides recommendations on soil-to-plant uptake factors that are relevant for these types of produce. The recommendations from this review have been considered in the derivation of a residential A HIL and are summarised below for the range of crops considered:
Produce Group     Plant Uptake Factors (mg/kg produce fresh weight per mg/kg soil)