Influence of race, tobacco use, and caffeine use on the relation between blood pressure and blood lead concentration.

A number of studies have suggested a small to moderate positive relation between blood pressure and blood lead concentration in males (2-4 mmHg/In(microgram/dl]. However, this 1986 study of San Francisco bus drivers suggests larger relations in black males (n = 132) for both systolic pressure (7.5 mmHg/In(microgram/dl] and diastolic pressure (4.7 mmHg/In(microgram/dl] at very low blood lead concentrations (2-21 micrograms/dl). This increase appears to result from negative confounding, particularly after taking into account tobacco use. Relations are even larger in blacks who infrequently use caffeine (16.7 and 10.4 mmHg/In(microgram/dl) for systolic and diastolic pressure, respectively). In contrast, a negative relation between systolic pressure and blood lead concentration (-5.7 mmHg/In(microgram/dl] is suggested in nonblack males (n = 117). These findings indicate that race, lead accumulation, and physiologic effects related to caffeine use (e.g., catecholamine effects) may interact to produce marked differences in effect on blood pressure.