Document ID: chunk:federal_register_of_legislation:F2013C00288:reg:5:p11
Version: federal_register_of_legislation:F2013C00288
Segment Type: reg
Provision Reference: reg 5 (pt 11/18)
Character Range: 3000020–3003229

Tuber vegetables                                                                             23                    59.8                                        28                    28
Tree fruit                                                                                   100                   140                                         100                   180
* Percentage of total vegetables or fruit, from EA (2009e)
** Calculated based on total vegetable and fruit intakes from Australian data (noted above)

5.3.5.2         Consumption of home-grown produce
Domestic or backyard food production is a relatively small contributor to overall food production in Australia, with the total annual home-grown fruit and vegetable crop representing 4.1% and 5.3% respectively (ABS 1995). However, a reasonably large proportion of households engage in home food production, with 35% of households producing one or more vegetable types and 36% producing one or more types of fruit (ABS 1995). Any estimate of national behaviour is likely to be somewhat misleading; in particular, the differences between urban and rural populations are likely to be significant.

An average of 10% of vegetable and fruit consumption from home-grown produce has been applied as an appropriate generic estimate for HIL A.

It is noted that the consideration of separate intakes derived for home-grown fruit and vegetable crops in addition to background dietary intakes results in some double counting of fruit and vegetable ingestion and intakes derived from these sources. This has been addressed for each contaminant where plant uptake is considered significant, as noted in Appendix A.

5.3.5.3         Plant uptake factors
Perhaps the greatest uncertainty in determining uptake of a contaminant in produce is selecting the plant uptake or concentration factors (CFy) (MfE 2011b). Plants can accumulate contaminants via a number of pathways, the most important of which is typically absorption by roots where, depending on the nature of the contaminant, translocation to other portions of the plant may occur. Uptake of organic contaminants and metals occurs predominantly from the soil solution. Normally the concentration of a contaminant measured in the soil solution represents only a fraction of the total contaminant present in the soil. The ratio of the concentration in soil solution to the total in soil depends on a number of factors including soil pH, redox potential, soil organic matter, and soil texture. In soils and sediments where the clay content is relatively low, the availability of organic contaminants is strongly related to the fraction of organic carbon present (MfE 2011b).

Review of plant uptake models/approaches by MfE (2011b) indicated that, for organics, a range of simple and complex models are available. The review notes work done by EA (2006) where a number of models for the uptake of organic compounds in plants were reviewed.

A number of limitations were identified including the limited range of compounds tested (namely PAHs, PCBs and dioxins) and problems with study data (in reporting dry or fresh weight and whether data was from roots, shoots, fruits or tubers), highlighting