Site Mitigation & Restoration Program

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Human and Ecological Risk Office

Chemicals of Emerging Concern

Chemicals of Emerging Concern

The U.S. currently has more than 80,000 chemicals in commerce.  Of these, approximately 2,500 are “high production volume” (HPV) chemicals, which are manufactured at a rate of more than one million pounds annually, with nearly 45 percent of these HPV chemicals lacking adequate toxicological studies conducted to evaluate their health effects on humans and on wildlife.  Further, about 2,000 new chemicals are introduced into commerce annually in the U.S., at a rate of about seven new chemicals a day. 

Many in the US assume that the government carefully reviewed the safety of every chemical before it is allowed on the market. However, this assumption is not correct. In fact, most of the 80,000+ chemicals registered for use today have not been tested for safety or toxicity by any government agency.  The Frank R. Lautenberg Chemical Safety for the 21st Century Act, passed by Congress and signed into law by President Obama in June 2016, is the first overhaul in 40 years of the Toxic Substances Control Act of 1976, the main nationwide law governing toxic chemicals. 

Because of the many chemicals in commerce and/or to which the public may be exposed, scientists have developed improved screening methods for determining the toxicity of chemicals in environmental and biological media. As these studies progress, scientists and toxicologists are identifying “chemicals of emerging concern” or “contaminants of emerging concern” or “CECs” that may pose health risks to human and/or ecological species.   Recent studies have shown that some of these chemicals bioaccumulate due to very long half-lives in the body and/or bioconcentration through the food chain. 

Chemicals of Emerging Concerns reflect limitations in the chemicals regulatory systems at the state, national, and international level. CECs are chemicals that have appeared on the radar screen because scientists have discovered that these chemicals have toxicities not previously recognized, are found to be building up in the environment, are found to be accumulating in the bodies of humans and/or wildlife, and may have the potential to cause adverse effects on public health or the environment. 

Chemicals of Emerging Concern include many different compounds with potential significant impacts on human and the environment, including: Per- and Poly-fluoroalkyl substances, including perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), brominated and organophosphate flame retardants,  nitrosodimethylamine,  nanoparticles,  synthetic musks and other personal care product ingredients, perchlorate, nitrates, industrial chemical additives, stabilizers, adjuvants and hormonally-active compounds. 

For example, Perfluorinated compounds, including PFOA, and PFOS were used in firefighting foams, commercial household products including water and stain-repellent fabrics, nonstick products (i.e., Teflon), polishes, waxes, and paints, as well as in chrome plating facilities. Subsequent to the widespread use and distribution of these perfluorinated compounds, research emerged showing that these compounds posed a risk to human health. PFOA and PFOS have a long half-life in the body and bioaccumulate. PFOA, PFOS and other perfluorinated compounds have been identified in groundwater at many locations, including manufacturing sites, and firefighting sites.  Although US EPA has not issued a Maximum Contaminant Level (MCL), it has issued a lifetime health advisory of 70 parts per trillion PFOS and PFOA in drinking water supplies. Several states have established Notification Levels at similar or at considerably lower concentrations.  California has established Notification Levels (NL) of 13 parts per trillion for PFOS and 14 parts per trillion for PFOA. Due to these concerns, PFOA and PFOS are being replaced by shorter chain perfluoropolymers that may have a shorter half life in the body. 

Some Chemicals of Emerging Concern can also act as endocrine disruptors or gender-bending compounds that can disrupt normal hormonal function, reproductive development and function. Such CECs include a number of hormonally active or endocrine disrupting chemicals including pharmaceuticals and pharmaceutical wastes, bis-phenol-A and its substitutes, phthalates, nonylphenols and other compounds.  Emerging research shows that exposure to such hormonally-active chemicals during fetal, infantile or pubertal development may effect reproductive development and function during adulthood.

For example, Diethylstibesterol (DES) is a potent estrogen that was prescribed to millions of pregnant women from the 1950s to the early 1970s, supposedly to prevent misscariage, although later data showed the opposite.  When some of the first daughters exposed prenatally to DES started reaching puberty it was discovered that these “DES Daughters” showed a high frequency of a rare vaginal cancer, clear cell adenocarcinoma (CCA). Subsequent studies showed that these and many other DES daughters that followed them showed increases in reproductive tract abnormalities and cancers, as well as increased incidences of breast cancer, infertility, and pregnancy complications.  While DES was initially used with limited information on its long-term safety, as data emerged, it gained recognition as a Chemical of Emerging Concern with endocrine disrupting effects.  

Some endocrine disrupting chemicals, including estrogenic compounds and BisPhenol A, have been shown to exert Epigenetic effects. Depending on the chemical and timing of exposure, Epigenetic effects of Endocrine Disrupting Chemicals include changes in the structure of chromatin and DNA methylation that result in long-term changes in gene expression, cell growth and changes in susceptibility to maladies including diabetes, breast cancer and prostate cancer.  Due to concerns that chemicals may have endocrine disrupting effects US EPA initiated the Endocrine Disruptor Screening Program (EDSP).

Furthermore, exposure to some CECs in utero can exert transgenerational effects, in other words, – effects that are transmitted not only to the offspring, but are also transmitted for several generations thereafter. 

Surveys of natural and synthetic chemicals in urban watersheds have shown the widespread occurrence of chemicals that can cause effects in humans and in ecological species. Research has also shown Chemicals of Emerging Concern at many Federal Facility sites.

Note that as Chemicals of Emerging Concern are identified, and when exposures indicate that a CEC may be causing harm to human and/or ecological species, there may be efforts to further investigate and in some cases, to regulate such CECs.     

Additional information on these and other contaminants of emerging concern can be found in the links below.  These outside links are provided as source of information and are not necessarily endorsed by DTSC or HERO.