Citation:

DeflorioBarker, S., A. Egorov, G. Smith, M. Murphy, AND E. Hilborn. Drinking Water Source and Pulmonary Isolation of Nontuberculous Mycobacteria. Water Microbiology, Chapel Hill, North Carolina, May 14 - 16, 2019.

Impact/Purpose:

Nontuberculous mycobacteria (NTM) are potentially drinking waterborne contaminants and are associated with human infections. Other potential sources of NTM infection have been identified in case studies and include soil, ambient water and surface water. We evaluate the occurrence of NTM pulmonary isolation in a defined population and geographic area - three counties in central North Carolina. We evaluate associations between NTM isolation and source of drinking water along with other environmental exposures. NTM commonly includes Mycobacterium avium, a pathogen included on recent drinking water Contaminant Candidate Lists. As NTM is only transmitted from the environment, work such as this, designed to identify potential sources of human exposure to NTM at the population level, will support Program Office regulatory decision-making.

Description:

Background Acquisition of pulmonary nontuberculous mycobacteria (NTM) is primarily associated with environmental exposures. Isolation prevalence increases with age. Rates of pulmonary isolation are increasing in the United States. Human NTM isolation and infection are associated with exposure to soil and contaminated water, including ambient water, healthcare-associated water, and drinking water. We evaluated the association between NTM pulmonary isolation and environmental risk factors including drinking water supply among North Carolina residents. Methods Reports of patients with pulmonary NTM isolation during 2006-2010 (cases) were collected from state public health records, hospitals and clinical laboratories among three counties in central NC. This analysis was conducted at the census block level (n=13,495 blocks) and was restricted to cases with geocoded residences. Negative binomial regression models with thin-plate spline function of geographic coordinates were applied to assess effects of public water supplies vs. private wells, and the presence of hydric (>20%) and acidic soils (>50%). Block-level demographic and geographic covariates evaluated in this analysis included: population size and density, housing price, race, age, land cover (trees, grass, impervious surface, wetland, surface water), and road network density. Results NTM cases (n = 507) were located in 462 (3.8%) blocks. Each additional year of median age at the block level was associated with 3.7% (95% CI: 2.9%, 4.5%) greater adjusted mean rate of isolation. Higher mean isolation rates were observed for: blocks with hydric soil: 29% (95% CI: 3.2%, 61%), p = 0.02, and those with acidic soil: 24% (95% CI: -3%, 59%), p = 0.09, after offsetting for population size and adjusting for median age, population density, proportions of developed land and wetland, and county. Drinking water source (public water supply vs. private wells) was not significantly associated with NTM isolation (p = 0.5). Discussion The observed significant statistical association between hydric soil and pulmonary NTM cases is consistent with previous reports of NTM isolation from peat-rich soils and wetlands. Drinking water source did not appear to be a risk factor for NTM isolation in this single metropolitan area with the majority of population served by three large public water supply systems. Further research is necessary to evaluate potential transmission of NTM via drinking water, and the role of other environmental risk factors. This abstract does not reflect EPA policy.

Record Details: