1. Secondary lead smelter workers showed significantly poorer performance scores than the nonexposed control groups." Decreased performance on block design, digit symbol, embedded figures, and Santa Ana (both hands). "A significant association between performance test scores and increased lead absorption was found... It is concluded that workers exposed to lead at levels considered 'safe' might be at risk of developing brain dysfunction with long term exposure." "Smelter groups, when compared with community groups, showed: lengthened choice reaction time in the order of 10 percent
2. Control for intellectual ability before exposure, especially in cross sectional studies, is particularly difficult. Nearly all studies used education, either to match group means in group comparisons, or as a covariate in multiple linear regression models. Several studies still found substantial differences between groups in vocabulary scores. This suggests that education may be an inadequate control for intellectual ability before exposure. For example, Baker et al found that exposure to lead had a strong negative association with the vocabulary test score.33 This may either represent a causal association or that less capable workers are most likely to work in the most highly exposed jobs. To the extent that the vocabulary score reflects overall intellectual ability before exposure, the difference found in this measure limits the inferences that can be made from other associations found
3. Schwartz Table S List of neurobehavioural tests that showed signficant differences between groups, or significant association with exposure variables (studies listed in approximate order of overall usefulness);Balbus-Komfeld, Stewart; BoMa
4. Association between performance and exposure variable Studies of moderate usefulness: Stollery et all30
5. picture completion subtest of WAIS; RT = reaction time; vis mem = visual memory; dig sp = digit span (F indicates forward only); voc = vocabulary subtest of WAIS; sim = similarities subtest ofWAIS; SA = Santa Ana coordination test (RH/LH denotes hand tested); ment conc = mental concentration subtest of WAIS; vis repro = visual reproduction subtest of WAIS; trail A/B = Trailmaking A or B; flick fus = flicker fusion test; symb copy = symbol copying; paired association lrn = paired associative learning subtest of Wechsler memory scale; vis gestalts repro = visual gestalts reproduction; obj ass = object assembly subtest of WAIS; perf IQ = performance IQ. t Abbreviations as for table 3. * NCV = nerve conduction velocity