Matthew Stanley Meselson conducted DNA and RNA research in the US during the twentieth and twenty-first centuries. He also influenced US policy regarding the use of chemical and biological weapons. Meselson and his colleague Franklin Stahl demonstrated that DNA replication is semi-conservative. Semi-conservative replication means that every newly replicated DNA double helix, which consists of two individual DNA strands wound together, contains one strand that was conserved from a parent double helix and that served as a template for the other strand. Meselson's work enabled researchers to better explain and control cellular development by showing how DNA are copied when a cell divides and interpreted when a cell makes proteins.

In March 1996, the National Academy of Sciences of the United States released 'Veterans and Agent Orange Update 1996: Summary and Research Highlights,' which summarized research on the health effects of Agent Orange and other herbicides used in the Vietnam War. In their 1996 report, the National Academy connects Agent Orange exposure with two health conditions: spina bifida, a birth defect that occurs when the spinal cord develops improperly, and peripheral neuropathy, a nervous system condition in which the peripheral nerves are damaged. Spina bifida was the first birth defect to linked to Agent Orange exposure. The resulting disability compensation for affected children, as a result of the conclusions in the 1996 report, marked the first time that the US Veterans Administration addressed the health outcomes of veterans' families, and not exclusively veterans themselves.

Sprayed extensively by the US military in Vietnam, Agent Orange contained a dioxin contaminant later found to be toxic to humans. Despite reports by Vietnamese citizens and Vietnam War veterans of increased rates of stillbirths and birth defects in their children, studies in the 1980s showed conflicting evidence for an association between the two. In 1996, the US National Academy of Sciences reported that there was evidence that suggested dioxin and Agent Orange exposure caused spina bifida, a birth defect in which the spinal cord develops improperly. The US Department of Veterans Affairs' subsequent provision of disability compensation for spina bifida-affected children marked the US government's first official acknowledgement of a link between Agent Orange and birth defects. By 2016, spina bifida and related neural tube defects were the only birth defects associated with Agent Orange.

Spina bifida is a birth defect that affects the spines of developing fetuses and infants, and research in the 20th century indicated that chemicals in the herbicide Agent Orange likely lead to the birth defect. People with spina bifida can have nerve damage, paralysis, and mental disabilities. During the Vietnam War in the 1960s, the US military employed Agent Orange and other herbicides to destroy enemy crops and forest cover until 1970. Though studies of the link between Agent Orange exposure and birth defects were at first inconclusive, in 1995 the US National Academy of Sciences concluded that one birth defect, spina bifida, was associated with paternal Agent Orange exposure. Spina bifida was, by the twenty-first century, the only birth defect that the US Veterans Administration connected to Agent Orange exposure.

In 1984, J. David Erickson and his research team published the results of a study titled 'Vietnam Veterans' Risks for Fathering Babies with Birth Defects' that indicated that Vietnam veterans were at increased risk of fathering infants with serious congenital malformations, or birth defects. Researchers at the Centers for Disease Control (CDC) in Atlanta, Georgia, conducted the study to address Though the study's results were inconclusive, the study was one of the first to document a possible association between Vietnam War service and spina bifida, a lower back birth defect in which the spinal cord does not form properly. Later research established the links between Agent Orange exposure and various birth defects and led the US Department of Veterans Affairs to offer disability compensation for Vietnam veterans and their families who were affected by Agent Orange exposure.

In the legal case In re Agent Orange Product Liability Litigation of the early 1980s, US military veterans of the Vietnam War sued the US chemical companies that had produced the herbicide Agent Orange, and those companies settled with US veterans out of court. Agent Orange contains dioxin, a chemical later shown to disrupt the hormone system of the body and to cause cancer. As veterans returned to the US from Vietnam, scientists further confirmed that exposure to Agent Orange caused a variety of cancers in veterans and developmental problems in the veterans' children. The veterans and their families held the chemical manufactures of Agent Orange liable for their injuries and the injuries to their children. The chemical companies settled the case out of court in 1984 for $180 million, to be used for medical expenses or compensation for death relating to veterans' exposure to Agent Orange. Agent Orange's use in the Vietnam War affected close to ten million people in the US, including members of the US military directly exposed to it, and their children conceived years after direct exposure.

In 1988, the US Centers for Disease Control published 'Health Status of Vietnam Veterans III. Reproductive Outcomes and Child Health,' which summarized part of the results of the Vietnam Experience Study commissioned by US Congress to assess the health of US Vietnam veterans. They published the article in the Journal of the American Medical Association. The most heavily used herbicide in the Vietnam, Agent Orange, had previously been found to contain a contaminant linked to birth defects in rats. By comparing the health of Vietnam War veterans exposed to Agent Orange in Vietnam to those serving elsewhere, researchers determined that veterans who served within Vietnam more frequently reported health problems for themselves and their children, but were not at increased risk of fathering children with birth defects. Later studies overturned that latter conclusion and definitively linked Agent Orange exposure to later birth defects. The article represented the first attempt by the US government to ascertain the full risk of birth defects posed by Agent Orange, which eventually culminated in 1997 when the US Veterans Administration compensating the families of Vietnam veterans for Agent Orange-related birth defects.

Arthur W. Galston studied plant hormones in the United States during the late-twentieth century. His dissertation on the flowering process of soybean plants led others to develop Agent Orange, the most widely employed herbicide during the Vietnam War, used to defoliate forests and eliminate enemy cover and food sources. Galston protested the spraying of those defoliants in Vietnam, as they could be harmful to humans, animals, and the environment. Toxicological research conducted in 1967 revealed that Agent Orange contained a synthetic compound called dioxin, an accidental pollutant that caused birth defects, which led to the discontinuation of Agent Orange in Vietnam in 1971. Galston’s predictions of Agent Orange’s toxicity were confirmed in the 1980s when studies linked Agent Orange to the illnesses of Vietnam veterans and to their children.

My Father, My Son is a dual autobiography by father and son Elmo Russell Zumwalt Jr. and Elmo Russell Zumwalt III published by Macmillan Publishing Company in 1986, detailing their experiences during the Vietnam War and particularly with Agent Orange, an herbicide used for defoliation and crop destruction during the war. As a commander in the Navy, Zumwalt Jr. ordered the use of Agent Orange in South Vietnam, where Zumwalt III was stationed. In the 1980s, Zumwalt III was diagnosed with two cancers, non-Hodgkin's lymphoma and Hodgkin's disease, and his son, Elmo Russel Zumwalt IV, was diagnosed with a learning disability. Zumwalt III and his father co-wrote My Father, My Son to argue that Agent Orange caused their family's medical problems. contributing to a public discussion of what should be done for those exposed to Agent Orange.