Chemical Exposures at Naval Air Facility Atsugi
During the operation of the Shinkampo incinerator complex, the Department of the Navy conducted extensive environmental sampling and health risk assessments to evaluate potential exposures affecting the base population. These efforts included:
Multiple air and soil sampling campaigns (1988 to 2001)
Two screening human health risk assessments (1995, 1998)
A comprehensive human health risk assessment (2002)
VFEA evaluated all available sampling data and identified nearly 290 chemicals detected in ambient air and soil across the studies. Based on maximum detected concentrations, 83 of these chemicals would be classified as contaminants of concern under current EPA screening levels and ambient air standards.
Soil
21 contaminants of concern were identified in the soil.
8 chemicals exceed EPA Regional Screening Levels (RSLs) for cancer
16 chemicals exceed EPA RSLs for non‑cancer effects
3 chemicals exceed both cancer and non‑cancer RSLs
Ambient Air
70 contaminants of concern were identified in ambient air.
38 chemicals exceed EPA RSLs for cancer
53 chemicals exceed EPA RSLs for non‑cancer effects
26 chemicals exceed both EPA cancer and non‑cancer RSLs
6 chemicals exceed EPA National Ambient Air Quality Standards (NAAQS) for criteria pollutants.
EPA RSLs: U.S. Environmental Protection Agency Regional Screening Levels (RSLs) are risk-based chemical concentration values developed by the EPA to help identify contaminants in air, soil, and water that may warrant further investigation or cleanup; values are conservative health-protective screening tools, not regulatory standards.
EPA Cancer RSL (Target Risk = 1E‑06): EPA screening levels for cancer based on a lifetime excess cancer risk of 1 in 1,000,000.
EPA Noncancer RSL (Target Hazard Quotient = 0.1): EPA non‑cancer screening levels based on 10% of the reference dose (HQ = 0.1); used to account for cumulative risks from multiple chemicals.
EPA NAAQS: EPA National Ambient Air Quality Standards are federal outdoor air quality standards for certain criteria pollutants set to protect public health with an adequate margin of safety.
ATSDR MRL: ATSDR Minimal Risk Levels are health‑based screening values for non‑cancer effects; exceeding an MRL indicates a need for further evaluation, not that adverse effects will occur.
Contaminants of Concern in Ambient Air
The following links highlight the contaminants of concern identified in each study:
While the contaminant of concern lists remain applicable, they are no longer current as they were published two to three decades ago and relied on scientific assumptions, toxicity values, exposure factors, and analytical methods developed primarily in the 1980s and 1990s. Since that time, there have been substantial advances in toxicological science and exposure assessment, as well as a more refined understanding of the long-term and cumulative health effects associated with incinerator-related contaminants such as dioxins, metals, particulate matter, and other combustion byproducts. If the 2002 final health risk assessment were to be updated today there would be additional contaminants of concern.
Ultimately, the health risk assessment should be updated using current methodologies and the latest toxicological data to provide a more refined, accurate, and up-to-date characterization of potential health risks.
Water Sampling
NAF Atsugi's drinking water is drawn from production wells on base that tap into two shallow, unconsolidated sand-and-gravel aquifers directly beneath the installation — the Sagamino Gravel Layer (SGL) and the Zama-Kyuryo Gravel Layer (ZGL). The SGL begins at roughly 10–56 feet (3–17 m) below the surface and is overlain only by Kanto Loam — a permeable volcanic ash deposit that actively recharges the underlying gravel aquifer and provides little meaningful protection against infiltration of fuel, solvents, or other volatile contaminants. The ZGL is a somewhat deeper, older Pleistocene terrace deposit, encountered at approximately 66–102 feet (20–31 m) below the surface. Both are unconfined to semi-confined gravel aquifers, meaning they lack a thick, continuous clay or rock cap that would shield them from surface contamination; any spill of fuel, solvents, or firefighting foam on the base had a short, direct pathway down through the overlying permeable soils and into the drinking water supply.
NAF Atsugi Consumer Confidence Reports confirm that these vulnerabilities are not just theoretical. In the early 1990s, TCE was detected in local groundwater at levels exceeding the maximum contaminant level (MCL), prompting the installation of an air stripper at the water treatment plant to reduce concentrations. While the air stripper was relatively effective at removing TCE and other volatile organic compounds, exceedances continued to be recorded in 1994, 1995, 2006, and 2007. It is unclear how long TCE had been present in the drinking water prior to its discovery; given the absence of routine comprehensive groundwater sampling in preceding decades, it is plausible the contamination had been present for years, if not decades. Available water sampling also revealed exceedances of bis(2-ethylhexyl) phthalate in 2002 and consistent exceedances of lead throughout the years. Sampling for per- and polyfluoroalkyl substances (PFAS) in the water at NAF Atsugi did not begin until late 2020, at which point PFAS was detected above current EPA limits. Because major PFAS sources on military installations—particularly the widespread use of aqueous film-forming foam (AFFF) for firefighting and fire-training activities—date back to the 1970s, it is highly likely that PFAS contamination was present in the drinking water long before formal monitoring began.
The detection of TCE and PFAS in the base drinking water supply—both synthetic compounds with no natural occurrence—is strong evidence that the shallow aquifer was impacted by surficial contamination sources located on or near the installation. These findings, combined with the aquifer’s inherent physical vulnerability and the documented history of solvent handling, fuel releases, and AFFF use on base, suggest that groundwater contamination represented an ongoing—and potentially underrecognized—exposure pathway for decades both before and after operation of the incinerator complex.
We are concerned that residents and workers may have been exposed for years to trichloroethylene-contaminated drinking water prior to installation of the air stripper system in the early 1990s, as well as to PFAS contamination associated with decades of military activities. Available monitoring data indicate that PFAS continues to impact drinking water at NAF Atsugi at concentrations exceeding levels the EPA considers protective of human health.
A FOIA request submitted by VFEA for NAF Atsugi water quality reports revealed that the Navy could only provide records dating back to 1989 — and even those were incomplete and sporadic. Records from 1989 through the mid-1990s were fragmentary, consisting largely of a limited number of lead sampling reports, with significant gaps that may reflect incomplete record retention. Records requested for the years prior to 1989 were either not located or no longer exist, leaving the full history of water quality monitoring at the installation prior to this period unverifiable. Whether these gaps are the result of lost documentation or reflect the absence of routine, systematic sampling altogether prior to the 1990s remains an open question — one with significant implications for understanding the extent of potential chemical exposures experienced by personnel and their families stationed at NAF Atsugi during that era.