Cadmium provisional tolerable weekly intake

In order to prevent any further increase of cadmium in agricultural soils likely to increase the dietary intake of future generations, the WHO recommended that airborne levels of cadmium in rural areas should be as low as possible and not exceed 5 ng/m and in urban or industrial areas levels should not exceed 10 ng/m (WHO, 1994). The provisional tolerably weekly intake (PTWI) for the total cadmium intake was set at 7 p.g/kg of body weight (WHO, 1989). A guideline value for cadmium in drinking water of 3 p.g/1 was established based on an allocation of 10% of the PTWI (WHO, 1993,1996). 

In 2004 the Joint Food and Agriculture OrganizationAVorld Health Organization Expert Committee on Food Additives (JECFA) recommended the provisional tolerable weekly intake of cadmium as 0.007 mg/kg body weight [15]. Also the WHO (in 2004) adopted the provisional guideline of 0.003 mg/L for cadmium in drinking water [15]. In addition, a 2007 WHO publication recommended the limit of cadmium in herbal medicines and products to be 0.3 mg/kg [16]. 

The level of 400-500 ug of cadmium indicated as the provisional tolerable weekly intake is based on calculations involving normal and critical values of cadmium in the renal cortex and on what is known of the rate of accxamulation of cadmium in that organ. However, the uncertainties involved are many and varied. For example, the cadmium intake of many populations is presently unknown only scanty data are available on the absorption and excretion of cadmium in various nutritional and metabolic states and it is not very well established that populations with excessive cadmium loads from the diet inevitably develop proteinuria. 

The toxicity of cadmium has been known for more than 150 years, as summarized recently by Nordberg [1] nevertheless, there is stiU an ongoing discussion on cadmium-induced toxicity at comparatively low exposure conditions. With respect to non-cancer endpoints, the European Food Safety Authority (EFSA) has lowered the Provisional Tolerable Weekly Intake (PTWI) of 7 pg/kg bw established previously by the Joint FAOAVHO Expert Committee on Food Additives to a TWI of 2.5 pg/kg bw based on cadmium-induced nephrotoxicity [2]. One other endpoint of toxicological concern on low exposure conditions of the general population... 

In Tab. 10-1 the calculated number of samples n required is demonstrated for probabilities of an error of the first kind of a = 0.1 and a = 0.25. With the exception of cadmium and lead the number of samples required is less than or equal to 10 for a probability of an error of the first kind of 25%. When the intake is well below the provisional tolerable weekly maximum, as in the case investigated [HAHN et al., 1992], the sample size for representative assessment can be reduced considerably. 

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