Objective: Examine the potential role of lead in water as a risk factor for PD.

Background: Studying disease rates in different locations is an established method to investigate diseases of unknown etiology. For example, high mesothelioma rates in U.S. maritime states identified shipbuilding as a risk factor for mesothelioma and exposure to asbestos as the cause [1].   We examined PD prevalence rates in U.S. states in relation to suspected risk factors involving lead (Pb).

Pb is a known neurotoxin that is implicated in PD [2].  The major route of Pb exposure is dietary, and a major source is Pb is water.  Pb enters water supplies via surface and groundwater and via plumbing.  We examined PD prevalence in U.S. states in relation to two sources of aqueous Pb:  data on Pb in water samples by state published by the EPA, and the number of “lead service lines”, i.e., the lead pipes that connect homes to municipal water supplies per state.  Presently, there are more than 6,000,000 lead service lines in use in the U.S.

Method: PD prevalence data by state, adjusted for age, race and sex, were obtained from Mantri et al. [3].  First, we obtained Pb values from water samples between 1990-2010 from the EPA Water Quality Portal. Linear models were run with PD prevalence as a function of water Pb levels for untransformed and log-transformed data. Second, we examined the prevalence of lead service lines using data from the 2016 National Survey of Lead Service Line Occurrence.  Exposure to lead service lines is an established surrogate for Pb levels in blood [4].  Data were analyzed by multiple regression with PD prevalence as a function of lead service lines, controlling for other identified risk factors, e.g., acid rain [5].

Results: State-level Pb levels measured in groundwater did not predict PD.  Conversely, the number of lead service lines was a highly significant predictor of PD (p<0.0001) even after adjusting for potential confounding factors (p=0.002).  The prevalence of lead service lines accounted for more than half the variance in PD prevalence rates in US states.

Conclusion: Our findings on lead service lines provide support for Pb in PD etiology.  Analytic epidemiologic studies of Pb in water are merited.

References: [1] Blot WJ, Stone BJ, Fraumeni JF Jr, Morris LE. Cancer mortality in U.S. counties with shipyard industries during World War II. Environmental Research 1979 Apr;18(2):281-90. doi: 10.1016/0013-9351(79)90105-1. PMID: 510250.
[2] Kuhn W, Winkel R, Woitalla D, et al. High prevalence of parkinsonism after occupational exposure to lead-sulfate batteries. Neurology 1998 Jun;50(6):1885-1886. DOI: 10.1212/wnl.50.6.1885. PMID: 9633752.
[3] Mantri S, Fullard ME, Beck J, Willis AW. State-level prevalence, health service use, and spending vary widely among Medicare beneficiaries with Parkinson disease. NPJ Parkinson’s Disease 2019: 5: https://doi.org/10.1038/s41531-019-0074-8.
[4] Brown MJ, Raymond J, Homa D, et al. Association between children’s blood lead levels, lead service lines, and water disinfection, Washington, DC, 1998-2006. Environmental Research 2011 Jan;111(1):67-74. DOI: 10.1016/j.envres.2010.10.003. PMID: 21112052.
[5] Schwartz GG, Williamson MR. Acid precipitation and the prevalence of Parkinson’s disease: An ecologic study in U.S. States. Brain Sciences 2021 Jun 12;11(6):779. doi: 10.3390/brainsci11060779. PMID: 34204597; PMCID: PMC8231258.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/an-ecologic-study-of-aqueous-lead-exposure-and-parkinsons-disease/