Chemistry Reference
In-Depth Information
to be balanced against its toxic effects. In the past, risk
assessment of the toxic effects of EMs has sometimes
been developed separately from those for defi ciency,
and confl icting recommendations have occurred. To
avoid such a situation, explicit methods that use a
combined approach have been developed and dis-
cussed by Mertz (1994), Nordberg and Skerfving
(1993), WHO (1996), (Oskarsson, 1995), Mertz (1998),
Olin (1998), Sandstrom (1998), Nordberg
et al.
(2000),
IOM (1998, 2001), and WHO/IPCS (2002). Some
aspects from those documents will be summarized
and discussed in this chapter. Considerable weight
is given to the principles described by WHO/IPCS
in the Environmental Health Criteria Document on
Principles and Methods for Assessment of Risk From
Essential Trace Elements (WHO/IPCS, 2002).
The acceptable range of oral intake (AROI) is
designed to limit defi cient and excess intakes in healthy
populations and is set for different age-sex groups and
physiological states such as pregnancy and lactation.
To facilitate comparisons, AROIs are discussed in rela-
tion to other risk assessment approaches. The prin-
ciples and methods used to develop an AROI for an
EM are not necessarily applicable to toxic nonessential
metals or other chemicals.
A number of abbreviations and acronyms used in
this chapter are given in Table 1. IUPAC offi cial recom-
mendations (Nordberg
et al.
, 2004) for defi ning some of
these key terms are given below.
Acceptable daily intake, ADI
Estimate by JECFA of the amount of a food additive,
expressed on a body weight basis, that can be in-
gested daily over a lifetime without appreciable
health risk.
Note 1: For calculation of ADI, a standard body mass
of 60 kg is used.
Note 2: Tolerable daily intake (TDI) is the analogous
term used for contaminants.
Tolerable daily intake, TDI
Estimate of the amount of a potentially harmful sub-
stance (e.g., contaminant) in food or drinking wa-
ter that can be ingested daily over a lifetime with-
out appreciable health risk.
Note: Acceptable daily intake (ADI) is normally used
for substances not known to be harmful, such as
food additives.
Tolerable weekly intake, TWI
Estimate of the amount of a potentially harmful
substance (e.g., contaminant) in food or drinking
water that can be ingested weekly over a lifetime
without appreciable health risk.
Toxicity
1. Capacity to cause injury to a living organism de-
fi ned with reference to the quantity of substance
administered or absorbed, the way in which the
substance is administered and distributed in
time (single or repeated doses), the type and se-
verity of injury, the time needed to produce the
injury, the nature of the organism(s) affected, and
other relevant conditions.
2. Adverse effects of a substance on a living organ-
ism defi ned as in 1.
3. Measure of incompatibility of a substance with
life: this quantity may be expressed as the recip-
rocal of the absolute value of median lethal dose
(1/LD
50
) or concentration (1/LC
50
).
TABLE 1
List of Abbreviations and Acronyms
ADI
acceptable daily intake
AROI
acceptable range of oral intake
BMD
benchmark dose
CV
coeffi cient of variation
DRI
dietary reference intakes
EM
essential metal
FAO
Food and Agriculture Organization, United Nations
IUPAC
International Union of Pure and Applied Chemistry
JECFA
Joint Expert Committee on Food Additives,
United Nations
LOAEL
lowest- observed-adverse-effect level
PRI
population reference intake
PTDI
provisional maximum tolerable daily intake
2 BASIC CONCEPTS
PTWI
provisional tolerable weekly intake
RDA
recommended dietary allowance
2.1 Defi nition of an AROI (Acceptable
Range of Oral Intake)
Considerable interindividual variation exists
in the human population. For an essential metal,
this applies to the expression of toxic effects from
higher doses and the expression of adverse effects
of deficiency from too low intakes. In Figure 1, this
interindividual distribution of sensitivity is shown
RfD
reference dose (oral)
SCF
EU Scientifi c Committee on Food
SD
standard deviation
SF
safety factor
SRPMI
safe range of population mean intake
TDI
tolerable daily intake
TI
tolerable intake
TWI
tolerable weekly intake
UL
tolerable upper intake level
