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Table 5 Quantitative evaluation on intraspecies differences between adult and the young

From: Dispelling urban myths about default uncertainty factors in chemical risk assessment – sufficient protection against mixture effects?

Substances dataset Dose metric Stage of development Results Reference
Animal data
238 chemicals LD50 Adult and newborn mammals Median LD50Adult/LD50Newborn = 2.6 [70]
    14% of ratios exceeded 10  
18 industrial chemicals pNOAEL Young and newborn rats (postnatal days 4 to 21) NOAELYoung/NOAELNewborn < 5 for 17 of 18 chemicals [98]
Human data
15 anticancer drugs MTD Adults and children 1.3 < Mean MTDChild/MTDAdult <4.1 [99], ratio of equivalent doses in mg/kg calculated by Dourson et al. [100]
24 drugs Hepatic clearance (Cl) or half-life (HL) Adults and newborns Cl or HLNewborn/ Cl or HLAdult > 3.2 for 33% of drugs [101], ratios calculated by Dourson et al. [100]
22 substances Toxicokinetic parameters Adults and children and/or newborns 3.2 subfactor for toxicokinetics intraspecies differences adjusts the adult parameter to that of the infant or child for 91% of substances. [78] as calculated by Dourson et al. [100]
313 substances (mostly pharmaceuticals) LD50 Adults and children 14% of LD50Adult/LD50Child > 10 [102]
6 drugs Toxicokinetic parameters (one toxicodynamic) Adult and children Ratio of mean adult parameter to lower 95% value of children varied between 0.6-3.7. [92]
    Composite ratios all below 10  
44 drugs Half-life Adult and children in different age groups Proportion of children whose half-life exceed 3.2-fold the adult mean value; [94]
    0–1 week premature: 70%  
    0–1 week full term: 26%  
    1 week- 2 months: 27%  
    2 months-18 years: 0%