Study for Promotion of Health in Recycling Lead (SPHERL) is a prospective 2-year follow-up study of lead workers with exposure levels varying between and within individuals. SPHERL addresses to what extent between-subject differences or within-subject changes in lead exposure may have a measurable impact on blood pressure, the cardiovascular system, renal function, the autonomic nervous system, peripheral nervous conduction velocity, and neurocognitive function.

At the beginning of December 2015, 70 participants were included in the study.

Background

• Whether low-level lead exposure impacts on blood pressure, regulation of the cardiovascular system, glomerular or tubular renal function, sympathetic nervous modulation, peripheral nervous conduction velocity, and neurocognitive function remains uncertain.

Study Population

• SPHERL will enroll 500 lead recycling workers with changing lead exposure, who will be examined at baseline (2014-2015) and followed up at annual intervals for 2 years (2016-2017).

Methods

• Volunteers eligible for the study are (i) new and existing hires without previous occupational lead exposure who will be performing tasks with or without occupational lead exposure and (ii) existing hires with occupational lead exposure who will be transitioning to job tasks without occupational lead exposure within the next 2 years.
• Blood lead concentration will be the main biomarker of exposure.
• The main outcome variables are (i) blood pressure measured conventionally and by ambulatory monitoring, and analyzed as continuous or categorical variable, both cross-sectionally and longitudinally; (ii) indexes of glomerular and tubular renal function, (iii) heart rate variability analyzed in the frequency domain as measure of autonomous sympathetic modulation, (iv) peripheral nerve conductivity, (v) neurocognitive performance, (vi) and quality of life [the EuroQOL five dimensions (EQ-5D) questionnaire].

Expected Outcomes

• Assuming a 4-fold or higher surge in the blood lead concentration, the study is powered to demonstrate over 2 years an acceleration in the age-related rise of systolic blood pressure by 1 to 4 mm Hg or an increase of the coefficient of multiple determination (R2) from 0.22 to 0.24 by adding the change in the blood lead concentration to models relating changes in blood pressure to three other covariables. The longitudinal design of our study complies with the temporality principle of the Bradford-Hill criteria for assessing possible causality between outcomes and exposure.

Inclusion Criteria:

• Women and men are eligible.
• New hires without previous occupational lead exposure who will be performing tasks with lead exposure or current employees without previous occupational lead exposure moving to tasks with exposure.
• Informed written consent.

Exclusion Criteria:

• Pregnancy.
• Any serious health condition.

Participants will be recruited among the work force employed at lead recycling plants in North America.