delta-aminolevulinic acid dehydratase in low level lead exposure.

No statistically significant correlation was observed between log delta-aminolevulinic acid dehydratase (ALAD) activity and blood lead levels (Pb-B) in rural or urban habitants (p greater than .5 and P greater than .1, respectively) in whom no occupational source of lead was known. However, when the values the the two groups were pooled, there was a fairly good negative correlation (r = 0.509, P less than .01). Stepwise correlation coefficient analysis indicated the existance of a threshold value of Pb-B (around 15 mug/100 ml) below which ALAD activity had nor orderly relationship with the Pb-B. In contrast with married couples, parents and their children showed a remarkably high interrelationship in values of ALAD. It is concluded that in low level lead exposure primarily genetic factors influence the activity of ALAD and, thus ALAD is useful for the evaluation of lead exposure only when the lead level is higher than the threshold.