Assessing Cyanobacterial Harmful Algal Blooms as Risk Factors for Amyotrophic Lateral Sclerosis

Nathan Torbick,Beth Ziniti,Patricia L Henegan,Jim Haney,Xun Shi,Angeline Andrew,Ernst Linder,Walter Bradley,Elijah Stommel,Tracie Caller

doi:10.1007/s12640-017-9740-y

Abstract

Reoccurring seasonal cyanobacterial harmful algal blooms (CHABs) persist in many waters, and recent work has shown links between CHAB and elevated risk of amyotrophic lateral sclerosis (ALS). Quantifying the exposure levels of CHAB as a potential risk factor for ALS is complicated by human mobility, potential pathways, and data availability. In this work, we develop phycocyanin concentration (i.e., CHAB exposure) maps using satellite remote sensing across northern New England to assess relationships with ALS cases using a spatial epidemiological approach. Strategic semi-analytical regression models integrated Landsat and in situ observations to map phycocyanin concentration (PC) for all lakes greater than 8 ha (n = 4117) across the region. Then, systematic versions of a Bayesian Poisson Log-linear model were fit to assess the mapped PC as a risk factor for ALS while accounting for model uncertainty and modifiable area unit problems. The satellite remote sensing of PC had strong overall ability to map conditions (adj. R2, 0.86; RMSE, 11.92) and spatial variability across the region. PC tended to be positively associated with ALS risk with the level of significance depending on fixed model components. Meta-analysis shows that when average PC exposure is 100 μg/L, an all model average odds ratio is 1.48, meaning there is about a 48% increase in average ALS risk. This research generated the first regionally comprehensive map of PC for thousands of lakes and integrated robust spatial uncertainty. The outcomes support the hypothesis that cyanotoxins increase the risk of ALS, which helps our understanding of the etiology of ALS.

Highlights

Concern over toxins and public health threats resulting from cyanobacterial harmful algal blooms (CHABs) have gained attention as reoccurring seasonal blooms persist in many waters
& We carried out extensive field data collection to calibrate and validate satellite remote sensing of cyanobacterial harmful algal bloom extent and intensity across northern New England
The mapping outcomes show robust phycocyanin concentration (PC) mapping using Landsat ETM+ and Operational Land Imager (OLI) and in situ collected across multiple years, multiple path rows, seasons, and a range of lake conditions, indicating their usefulness for supporting public health investigations and CHAB tracking initiatives

Summary

Introduction

Concern over toxins and public health threats resulting from cyanobacterial harmful algal blooms (CHABs) have gained attention as reoccurring seasonal blooms persist in many waters. Cyanobacteria produce a variety of toxins that have human health implications, including beta-N-methyl-amino-L-alanine (BMAA) (Codd et al 2005). Two pathogenic mechanisms have recently been recognized both in sALS and familial cases: (1) protein misfolding (Mulligan and Chakrabartty 2013; Ogawa and Furukawa 2014; Grad and Cashman 2014; Ravits 2014), which is probably the major mechanism by which the cyanobacterial neurotoxin BMAA produces chronic neurotoxicity (Dunlop et al 2013), and (2) impairment of RNA metabolism (Robberecht and Philips 2013). Recent findings show that chronic dietary exposure of vervets to BMAA caused neurofibrillary tangles and amyloid deposits similar to those in the brains of patients with ALS/PDC in Guam, supporting the notion of BMAA as an environmental trigger (Cox et al 2016)

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