Human Developmental Effects
Impacts on Risk
People at different stages of life can respond very differently to environmental changes. Some changes to the environment resulting from climate change could alter normal human development both in the womb and later in life. Food borne illness and food insecurity, both likely outcomes of climate change , may lead to malnutrition. While adult humans exposed to mild famine usually recover quite well when food again becomes plentiful, nutritional reductions to a fetus in the womb appear to have lasting effects throughout life. Malnutrition and under nutrition in pregnant women are a global cause of low birth weight and other poor birth outcomes that are associated with later developmental deficits. Malnutrition is predominantly a problem in the developing world, but in the United States, one in six children still live in poverty, and other developed countries also have substantial populations with insufficient food resources and under nutrition that could be made worse by climate change. Climate change effects on food availability and nutritional content could have a marked, multigenerational effect on human development.
Changes in patterns and concentrations of contaminants entering the marine environment due to climate change will impact seafood species, many of which provide a major source of protein to global populations. Such contaminants, particularly metals such as mercury and lead that accumulate in fish and seafood, are a special concern for human developmental effects. Similarly, an increase in the use of herbicides and pesticides for agricultural purposes, as well as alterations in environmental degradation of such chemicals due to changes in climate, could result in increased exposures that would exceed safety guidelines and increase the risk of developmental changes. Other environmental exposures to pregnant women and to children that are associated with climate change also present hazards to normal human development. For example, certain commercial chemicals present in storage sites or hazardous waste sites can alter human development. Flooding from extreme weather events and sea-level rise are likely to result in the release of some of these chemicals and heavy metals, most likely affecting drinking and recreational waters. Some of these, including mercury and lead, have known negative developmental effects. And while more research is required, there is good reason for concern based on our current body of knowledge of certain toxic metals and persistent organic compounds. Of the metals likely to become more prevalent in human environments due to climate change, inorganic arsenic is of great concern because it is a potent human carcinogen, it alters the immune system, and it is a general poison that is lethal at certain doses. More than 100 million people worldwide are exposed to arsenic through groundwater contamination and industrial emissions. Both inorganic and methylated forms of arsenic have been shown to impede fetal development and increase spontaneous abortions. Persistent organic compounds, even those no longer in use in many locales such as DDT and PCBs, could increase in some human environments and decrease in others as a result of flooding and extreme weather events due to climate change. Many of the Superfund toxic waste sites in the United States contain PCBs and dioxins that have been linked to cognitive deficits in children that continue throughout their lives. It is expected that every person on the planet carries some body burden of PCBs, but people living near contaminated sites have greater exposures and an increased risk of disease. Dioxins, PCBs, asbestos, benzene, flame retardants, certain pesticides, and other chemicals are known to be immunotoxicants. Changes to the immune system during development can remain throughout life, possibly resulting in a reduced capacity to fight serious infection and an increased risk of several other diseases including cancer.