Glossary of Toxic Exposure Terms

Plain-language definitions of the chemical, environmental, and benefits terms used across this site.

TCE (Trichloroethylene)

TCE is an industrial solvent that was widely used to degrease metal parts and equipment, including at many military installations. It contaminated drinking water at bases such as Camp Lejeune, and the EPA classifies it as carcinogenic to humans, with the strongest evidence for kidney cancer and additional evidence linking it to non-Hodgkin lymphoma and liver cancer. Health effects depend on how much exposure a person had and for how long.

PCE (Perchloroethylene)

PCE, also called tetrachloroethylene or perc, is a solvent best known for its use in dry cleaning and metal degreasing. It was a major contaminant in Camp Lejeune's drinking water, largely from an off-base dry cleaner, and the EPA considers it likely to be carcinogenic to humans, with studies suggesting links to bladder cancer and other illnesses. Like TCE, it can persist in groundwater for decades.

PFAS (Per- and Polyfluoroalkyl Substances)

PFAS are a large family of thousands of synthetic chemicals, often called forever chemicals because they break down very slowly in the environment and in the human body. On military bases, the biggest source has been firefighting foam used in training and crash response. Research suggests links between certain PFAS and kidney cancer, testicular cancer, thyroid problems, and other health effects, though scientists are still studying many of these chemicals.

PFOS (Perfluorooctane Sulfonate)

PFOS is one of the oldest and most studied PFAS chemicals, and it was a key ingredient in the firefighting foam used on military bases for decades. U.S. manufacturers largely phased it out in the early 2000s, but it remains in soil, groundwater, and people's blood because it breaks down so slowly. Studies have associated PFOS exposure with immune system effects, cholesterol changes, and possibly certain cancers.

PFOA (Perfluorooctanoic Acid)

PFOA is a widely studied PFAS chemical once used to make nonstick coatings and found in some firefighting foams. The EPA has concluded that PFOA is likely carcinogenic to humans, and research has linked it to kidney cancer and other health effects. It was phased out of U.S. production but persists in the environment and is a common contaminant near military installations.

AFFF (Aqueous Film Forming Foam)

AFFF is a firefighting foam the military has used since the 1970s to put out fuel fires, both in emergencies and in routine training. It contains PFAS chemicals, and repeated use at fire training areas, hangars, and crash sites has contaminated groundwater at hundreds of installations. The Department of Defense is phasing out PFAS-based foams in favor of newer formulas.

PCBs (Polychlorinated Biphenyls)

PCBs are man-made chemicals that were used in electrical transformers, capacitors, hydraulic fluids, and other equipment until the U.S. banned their manufacture in 1979. They persist in soil and sediment for decades and build up in fish and animals. The EPA classifies PCBs as probable human carcinogens, and they have been found at many current and former military sites.

VOCs (Volatile Organic Compounds)

VOCs are chemicals that evaporate easily into the air, including solvents like TCE and PCE and fuel components like benzene. On military bases, VOCs from spills and disposal sites can contaminate groundwater and, in some cases, rise into buildings as vapor, a process called vapor intrusion. Health effects vary by chemical, dose, and length of exposure.

Benzene

Benzene is a chemical found in gasoline, jet fuel, and many solvents, so it is common around fuel storage, motor pools, and flight lines. It is a known human carcinogen, with strong evidence linking long-term exposure to leukemia, especially acute myeloid leukemia, and to other blood disorders. Benzene was one of the contaminants found in Camp Lejeune's drinking water.

Asbestos

Asbestos is a group of natural mineral fibers that was widely used in insulation, pipe coverings, brakes, and building materials, and it was especially common aboard Navy ships built before the 1980s. Breathing asbestos fibers can cause mesothelioma, lung cancer, and the scarring disease asbestosis, often decades after exposure. Veterans who worked in shipyards, construction, vehicle repair, or demolition may have had significant exposure.

Mesothelioma

Mesothelioma is a rare and aggressive cancer of the lining around the lungs or abdomen, and it is almost always caused by asbestos exposure. It often appears 20 to 50 years after exposure, which is why veterans are sometimes diagnosed long after leaving service. Veterans diagnosed with mesothelioma may qualify for VA benefits if their asbestos exposure happened during military service.

Dioxin

Dioxins are a group of highly toxic chemicals that form as unwanted byproducts of burning and some manufacturing processes. The most toxic form, TCDD, contaminated the herbicide Agent Orange used during the Vietnam era. Dioxins persist in the body and environment for years and have been linked to several cancers, type 2 diabetes, and other health problems.

Agent Orange

Agent Orange was a tactical herbicide the U.S. military used to clear vegetation, most heavily during the Vietnam War, and it was contaminated with the toxic chemical dioxin. VA presumes that veterans who served in certain locations and time periods, including Vietnam, the Korean DMZ, and some bases in Thailand and elsewhere, were exposed. A long list of conditions, including several cancers, type 2 diabetes, and high blood pressure, are presumptively connected to that exposure.

Burn Pit

Burn pits were large open-air areas where the military burned trash, plastics, medical waste, fuel, and other materials, especially at bases in Iraq, Afghanistan, and other Southwest Asia locations. The smoke contained a mix of chemicals, and while research on long-term effects is still developing, the PACT Act now presumes that many respiratory illnesses and cancers in veterans who served near burn pits are connected to that service.

Superfund

Superfund is the common name for the federal program, run by the EPA, that investigates and cleans up the nation's most contaminated land and water. Many current and former military installations are Superfund sites because of decades of fuel, solvent, and chemical disposal. Cleanups at these sites can take many years and are often handled jointly by the Department of Defense and the EPA.

National Priorities List (NPL)

The National Priorities List is the EPA's official list of the most serious contaminated sites in the country that qualify for long-term Superfund cleanup. More than 100 current and former military installations have been placed on the NPL, including Camp Lejeune. Being listed means a site gets a detailed investigation and a formal cleanup plan, though listing alone does not say how much any individual person was exposed.

CERCLA

CERCLA, the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, is the federal law that created the Superfund program. It gives the EPA authority to clean up contaminated sites and to require the parties responsible for the pollution, including federal agencies like the Department of Defense, to perform or pay for cleanups. Most environmental investigations at military bases follow the process this law lays out.

EPA (Environmental Protection Agency)

The EPA is the federal agency responsible for protecting human health and the environment. It sets legal limits for contaminants in public drinking water, evaluates the health risks of chemicals, and oversees Superfund cleanups, including those at military installations. EPA documents are a key source for understanding what contamination was found at a particular base.

ATSDR (Agency for Toxic Substances and Disease Registry)

ATSDR is a federal public health agency, closely tied to the CDC, that evaluates how hazardous substances at contaminated sites may affect people's health. It publishes plain-language fact sheets on toxic chemicals and conducts health studies, including the major water modeling and health research on Camp Lejeune. Its findings have shaped both VA benefits and federal legislation.

Presumptive Condition

A presumptive condition is an illness that VA automatically presumes was caused by military service for veterans who meet certain service requirements, such as serving in a specific place during a specific time period. If a condition is presumptive for you, you do not have to prove a direct link between your service and your illness, which removes one of the hardest parts of a claim. You still need a current diagnosis and qualifying service.

Service Connection

Service connection is VA's formal finding that a veteran's disability or illness was caused by, or made worse by, military service. It is the foundation of a disability compensation claim, and it can be established through direct evidence, through aggravation of an existing condition, or through a legal presumption like those in the PACT Act. Without service connection, VA cannot pay disability compensation for a condition.

VA Disability Rating

A VA disability rating is a percentage, from 0 to 100 in steps of 10, that reflects how much a service-connected condition affects your health and ability to work. The rating determines the monthly compensation amount and can affect eligibility for other benefits. When a veteran has multiple conditions, VA combines the ratings using its own formula, so the total is usually not a simple sum.

C&P Exam (Compensation and Pension Exam)

A C&P exam is an evaluation that VA schedules, with a VA clinician or a contracted examiner, to gather medical evidence about a condition you have claimed. The examiner documents your diagnosis, symptoms, and how the condition relates to your service, and VA uses that report when deciding your claim and rating. It is an evaluation for benefits purposes, not a treatment appointment, and missing one without rescheduling can delay or hurt a claim.

Supplemental Claim

A supplemental claim is one of VA's decision review options that lets you ask VA to look at a previously denied claim again by submitting new and relevant evidence. Many veterans denied before the PACT Act have used supplemental claims to be reconsidered under the newer presumptions. There is generally no deadline to file one, though filing within a year of a decision can protect your effective date.

PACT Act

The PACT Act, formally the Sergeant First Class Heath Robinson Honoring our Promise to Address Comprehensive Toxics Act, is a 2022 law that is the largest expansion of VA benefits for toxic exposure in decades. It added more than 20 presumptive conditions related to burn pits, Agent Orange, and other exposures, expanded VA health care eligibility, and required VA to give enrolled veterans regular toxic exposure screenings. Veterans denied benefits before the law may be able to reapply.

Camp Lejeune Justice Act

The Camp Lejeune Justice Act, passed as part of the PACT Act in August 2022, allowed people exposed to contaminated drinking water at Camp Lejeune for at least 30 days between August 1, 1953 and December 31, 1987 to file claims against the federal government, something that was previously barred. The law's two-year filing window closed in August 2024, and claims filed before that deadline are still being processed and litigated. This litigation is separate from VA disability benefits for Camp Lejeune veterans, which remain available.

BRAC (Base Realignment and Closure)

BRAC is the congressional process the Department of Defense has used since the late 1980s to close or consolidate military installations. Closed bases often cannot be transferred for civilian use until environmental contamination is investigated and cleaned up, which is why many former BRAC bases remain in long-term cleanup programs. Veterans who served at closed bases can still face questions about past exposures there.

Groundwater Plume

A groundwater plume is a body of contaminated water that spreads underground from a pollution source, such as a leaking fuel tank or a solvent disposal area. Plumes can slowly move toward drinking water wells, sometimes traveling beyond base boundaries into neighboring communities. Environmental agencies map and monitor plumes for years to track where contamination is going and whether cleanup is working.

Remediation

Remediation is the process of cleaning up contaminated soil, groundwater, or buildings to reduce risks to people and the environment. Common methods include removing contaminated soil, pumping and treating groundwater, and installing systems that keep vapors out of buildings. At large military sites, remediation can take decades, and some sites are managed with long-term monitoring and land use restrictions rather than complete removal of all contamination.

Toxic Exposure Screening

A toxic exposure screening is a brief set of questions, required by the PACT Act, that VA health care providers use to ask enrolled veterans about possible exposures such as burn pits, Agent Orange, contaminated water, and radiation. Every veteran enrolled in VA health care is offered the screening at least once every five years. The screening helps connect veterans to follow-up care, registries, and benefits information, and answering it does not by itself decide any claim.

Airborne Hazards and Open Burn Pit Registry

This VA registry documents veterans who may have been exposed to burn pit smoke, sand and dust, and other airborne hazards during deployments, mainly to Southwest Asia and Afghanistan, and it helps VA study long-term health effects. VA redesigned the registry in 2024 so that eligible veterans are generally included automatically based on deployment records, with the option to opt out. Joining or being included in the registry does not affect eligibility for VA benefits and is not required to file a claim.

VSO (Veterans Service Organization)

A VSO is an organization, such as the DAV, VFW, or American Legion, whose accredited representatives help veterans and families prepare and file VA claims and appeals. Their claims assistance is free, and many veterans find it valuable to have an experienced representative for exposure-related claims. You can find accredited representatives through VA's official accreditation search.

Nexus Letter

A nexus letter is a written medical opinion from a doctor or other qualified clinician explaining why a veteran's current condition is at least as likely as not related to something that happened during military service. It is most useful for conditions that are not on a presumptive list, where the veteran must show the link between exposure and illness. A strong nexus letter explains the medical reasoning, not just the conclusion.

Maximum Contaminant Level (MCL)

An MCL is the highest level of a contaminant that the EPA legally allows in public drinking water systems under the Safe Drinking Water Act. In 2024 the EPA finalized the first national MCLs for several PFAS chemicals, including very low limits for PFOA and PFOS, though compliance deadlines and some details have been subject to ongoing regulatory and legal review. MCLs apply to public water systems, so private wells near military bases are usually tested separately.

This page is for informational purposes only and is not medical or legal advice. Consult a qualified professional about your health or benefits.