[Relationship between lead concentration in the air and blood lead levels of people living and working in the centre of a city (Frankfurt blood lead study). II. Correlations and conclusions (author's transl)].

The correlation analysis of the relationship between blood lead levels and lead-in-air concentrations measured in three winter periods showed a highly significant association despite a generally loose dependence of the variables. The regression equations clearly show that there would be a finite residual blood lead value even with completely lead-free air. In the case of the populations exposed to motor traffic in this study, this residual blood lead value is 80--90% of the initial value prior to the decrease in immission. The regression equations, statistically yield results which compare convincingly with ones obtained from model calculations based on studies of metabolism and respiratory physiology. The correlation between the observed changes in blood lead and the initial absolute values of blood lead concentration demonstrates with high statistical certainty that the higher the initial level, the greater was the observed change. This type of association also implies that there is a lower limit value of blood lead below which the decrease in blood lead changes to an increase despite reduction of lead-in-air.