Pathways of inhalation exposure to manganese in children living near a ferromanganese refinery: A structural equation modeling approach

Abstract

Manganese (Mn) is both essential element and neurotoxicant. Exposure to Mn can occur from various sources and routes. Structural equation modeling was used to examine routes of exposure to Mn among children residing near a ferromanganese refinery in Marietta, Ohio. An inhalation pathway model to ambient air Mn was hypothesized. Data for model evaluation were obtained from participants in the Communities Actively Researching Exposure Study (CARES). These data were collected in 2009 and included levels of Mn in residential soil and dust, levels of Mn in children's hair, information on the amount of time the child spent outside, heat and air conditioning in the home and level of parent education. Hair Mn concentration was the primary endogenous variable used to assess the theoretical inhalation exposure pathways. The model indicated that household dust Mn was a significant contributor to child hair Mn (0.37). Annual ambient air Mn concentration (0.26), time children spent outside (0.24) and soil Mn (0.24) significantly contributed to the amount of Mn in household dust. These results provide a potential framework for understanding the inhalation exposure pathway for children exposed to ambient air Mn who live in proximity to an industrial emission source.

Keywords: Blood; Dispersion modeling; Dust; Hair; Structural equation model (SEM).

Figure 1:. Theoretical Pathway Model for Children’s Inhalation Exposure to Mn

Endogenous variables represented by ovals; Exogenous variables represented by rectangles; Dust Mn = Household Dust Mn

Figure 2:. Structural Equation Model for Children’s Inhalation Exposure to Mn

SEM Diagram with Standardized Path Coefficient estimates from the modified SEM model; Significant Coefficients in bold Endogenous variables represented by ovals; Exogenous variables represented by rectangles Dust Mn = Household Dust Mn