Environmental Exposures

Environmental exposures include all the chemicals and compounds we come in contact with. Every day, most of us encounter hundreds or even thousands of such substances. Many of these substances appear to be almost completely harmless, others potentially harmful but unlikely to get into our bodies in a large enough quantities, while others may be incredibly harmful, even in very small quantities. 

Pesticides- General

Pesticides are chemicals used in homes and agriculture to get rid of pests (i.e. to kill ants or other insects). If you work with pesticides, live near fields, or use pesticides in your home, you and your family could be exposed to pesticides, even if you can’t smell or see them. Pesticides can be harmful to people, especially pregnant women and small children. You should avoid contact with pesticides as much as possible.

What can I do if there are pests in my house?

  • Keep pests out by tightly sealing food and drinks in containers.
  • Block entry points used by pests.
  • Fix leaks.
  • Keep the kitchen clean.
  • Keep garbage in a garbage can with a lid.

What are the safest ways to use pesticides indoors? 

  • Read the label first.
  • Use less toxic methods such as boric acid. 
  • Keep children and toys away when applying pesticides.
  • Make sure the room is well ventilated, open windows if possible. 
  • Use traps instead of poison for rats and mice.
  • Use sticky traps (glue) instead of sprays for cockroaches.
  • Use baits and traps instead of sprays for ants. 
  • Keep pesticides in their original containers.

What should I do if I work in the fields? 

  • Use clothing that protects your full body.
  • Change out of work clothes and shoes before entering your car or home and leave work shoes outside.
  • Don not hug or carry your children until you have showered and changed out of work clothes.
  • Keep your car clean; vacuum often.
  • Store and wash work clothes separate from other clothes.
  • Wash your hands before leaving work and eating.

What can I do to protect my children if I live near an agricultural field?

  • Don’t let your children play in fields.
  • If workers are applying pesticides in fields near your home, don’t let your children or pets go outside. Keep windows and doors closed.
  • Wash your children’s hands often, especially when they come inside and before they eat.
  • Wash children's toys and blankets frequently. 
  • Keep your home clean and vacuum frequently. 
  • Wash fruits and vegetables thoroughly. 

CERCH Findings on Pesticides

  • CERCH's findings on pesticides are extensive and vary by category and type of chemical. For more information on specific findings see below or go to our publications page. 


Organophosphates (OPs)

OPs were developed after World War II, based on wartime nerve gases and are the most commonly used agricultural insecticide in the U.S., though their use is in decline. OPs have been banned for home use in the U.S. and have harmful effects on the nervous system. Though some believe that OPs break down quickly when exposed to light and air, no one has confirmed that OPs can fully degrade and they have been detected in soil and drinking water long after application. Exposure to large amounts of OPs are more harmful to human health than an equal amount of Organochlorines (OCs) discussed below.

CERCH Findings on OPs:


  • Eating organically-grown fruits and vegetables reduces exposure compared with eating conventionally-grown produce.*
  • Wearing protective gloves and clothing during agricultural work greatly reduces exposure.

- The CHAMACOS Health Outcomes Study

Mothers’ exposure to OPs during pregnancy is associated with:

  • Shorter duration of pregnancy. 
  • Poorer neonatal reflexes. 
  • Lower IQ and poorer cognitive functioning in children. 
  • Increased risk of attention problems in children.

- Maternal Organophosphate Pesticide Metabolites in Urine

  • The CHAMACOS cohort of pregnant women have levels of OP metabolite levels in urine 30-40% higher than U.S. average.
  • 14.8% of pregnant women in the CHAMACOS cohort may exceed health-based exposure benchmarks.
  • More than 78% of CHAMACOS women had detectable levels of at least one OP -specific metabolite, and > 30% had two or more.

- Organophosphate Pesticide Exposure Modeling

  • Biomarker comparisons and model results showed that women in the CHAMACOS cohort had a slightly higher intake of OPs compared to the US average.
  • Diet is likely the primary pathway for these OP exposures. 

Pesticides- DDT, PCBs, & Organochlorines 

A class of compounds that persist in the environment and in the bodies of humans and other animals long after their use.

What is DDT?

  • DDT was widely used as a pesticide in agriculture and insect control from the 1950s to the 1970s in the U.S.

What are PCBs?

  • PCBs  are oils that do not catch fire under conditions of extreme pressure or temperature, and were widely used in transistors, capacitors, and other electronics equipment during the 1950s to the 1970s in the U.S. 

Why are we concerned about DDT and PCBs?

  • Both last for years or decades in soil and lake sediment, where DDT often breaks down into DDE, a toxic compound that is extremely persistent.
  • DDT, DDE and PCBs persist in the human body, accumulating in fat and breast milk. Most Americans have detectable levels of DDE and PBCs in their bodies. Female mammals are generally less effected by these chemicals because they release them through breast feeding.
  • DDT, DDE, and PCBs have been associated with increased risk of cancer, developmental delays, and disruption of endocrine function, including thyroid hormones which are essential in fetal and child neurodevelopment.
  • The main source of human exposure to DDT, DDE and PCBs is through diet, particularly meat, dairy and fish. High concentrations of these compounds can be found in fatty, long-lived fish such as lake trout and catfish because, although they may be present in the water at extremely low concentrations, they bioaccumulate in aquatic organisms. The compounds become concentrated as they move up through the food chain, and due to their powerful resistance to degradation they have been detected in polar bears, marine mammals and humans in regions where neither compound has been used.

What is being done?

  • DDT was banned for use in the U.S. in 1973 and production of PCBs halted in 1977 due to growing concern about their increasingly-evident negative impacts on wildlife, human health and the environment.
  • The landmark 1962 book, Silent Spring by Rachel Carson, centered on DDT and other persistent pollutants as a source of environmental and public health concern. This book is credited with spurring the U.S. ban of DDT, as well as initiating the modern environmental movement.
  • DDT and PCB use and production were banned by the 2001 Stockholm Convention on Persistent Organic Pollutants with 170 signatory countries as of 2008. This ban constitutes an international environmental treaty that aims to eliminate or restrict the production and use of persistent organic pollutants.
  • An exception was made for DDT under the Stockholm Convention ban for the use of DDT to control mosquitoes that carry malaria, which infects 250 million and kills 880,000 people annually. DDT use is increasing in some countries where malaria is prevalent.

CERCH Findings on Organochlorines:

- The CHAMACOS Birth Cohort Study


  • Higher levels of DDT in mother’s blood during pregnancy were associated with:
    • Poorer mental development in their children at age 2. 
    • But not with neonatal neurodevelopment. 
    • But not with fetal growth.


  • Prenatal exposure to PCBs (organochlorine compounds) is associated with:
    • Altered thyroid hormone levels in mothers.
    • For certain PCBs, prenatal exposure was associated with neonatal thyroid hormone levels.

Personal Care Products- Phthalates, Parabens, Ozybenzone and Triclosan

The average person uses several products every day, women more than men and teens more than women on average. These products may result in exposure to hundreds or even thousands of chemicals. Research by CERCH and others shows that many of the chemicals in the products we put on our bodies get into our bodies through inhalation, skin absorption or ingestion.One of our top concerns is that some products may contain hormone disruptors, which are chemicals that mimic, block, or otherwise interfere with the natural hormones in our bodies. Some hormone disruptors have been associated with increased likelihood of reproductive disorders in boys, delays in neurodevelopment, and cancer. 

Personal Care Products

What regulations exist to protect consumers?

  • The Food, Drug, and Cosmetics Act of 1938 created the FDA to regulate food and drugs but the FDA has limited authority over cosmetics.

  • The FDA does not require pre-market testing for cosmetics.

  • The FDA foes not have the authority to recall most personal care products.
  • The cosmetics industry is largely responsible for ensuring products are safe and do not have to share their testing results with the FDA.

What are the health concerns potentially related to personal care products? 

  • Triclosan: commonly used as an antibacterial agent in soap and toothpaste, triclosan may act as a hormone disruptor.
  • Phthalates: found in many scented products, fragrance, nail polish and soft plastics, phthalates have been associated with estrogenic and antiandrogenic effects. 
  • Parabens: commonly used as a preservative in cosmetics like lipstick and foundation, parabens may act as weak estrogens. 
  • Oxybenzone: commonly found in sunscreens, oxybenzone may act as a hormone disruptor.
  • Heavy metals lead, cadmium and other toxic metals have been detected as contaminants in lipsticks. 
  • Formaldehyde: some ingredients in personal care products release small amounts of formaldehyde, a known carcinogen. 

CERCH Findings on Cosmetics:

In the HERMOSA Study, 100 teen girls living in Salinas, CA, tried using low-chemical alternative products found in local supermarkets and drug stores. After 3 days their urine test results showed: 

  • Triclosan levels decreased about 36%, on average. 
  • Oxybenzone levels decreased about 35%.
  • Common parabens decreased about 44%.
  • Diethyl phthalate  decreased about 28%.

*Liu et al, EHP, 2013

Plastics- Bisphenol A (BPA)

A chemical compound used to make certain kinds of plastics (polycarbonate plastics and epoxy resins). BPA is one of the world’s highest production chemicals, with more than 6 billion pounds produced annually.

Where does one encounter BPA?

  • Plastics containing BPA are found in all stages of our food production chain, as BPA-containing materials are commonly used to process and pack food.
  • BPA-containing products are found in almost all households in the U.S. and in many other countries.
  • BPA is used in a variety of products:
    • Water bottles and baby bottles made of polycarbonate plastics,
    • Toys,
    • Water supply pipe linings in homes and commercial properties,
    • Food can linings,
    • Medical devices,
    • Dental sealants,
    • Cash registers and ATM receipts.
  • Researchers are still learning about the ways that human bodies take in BPA, but the main route of exposure is thought to be eating food or drinking water stored in or processed with BPA-containing plastics, and dental sealants. Absorption through the skin or inhalation may also play a role in human exposure.

What are the health concerns of BPA? 

  • BPA has been shown to act as an endocrine disruptor that behaves like estrogen at low doses.
  • Animal Studies show BPA is associated with:
    • Altered sexual and reproductive development,
    • Altered brain structure and behavior,
    • Increased weight gain,
    • Earlier onset of puberty in females,
    • Increased incidence of asthma, diabetes, heart disease, and reproductive cancers,
    • Transgenerational genetic effects.
  • Animal studies suggest that periods of development, such as infancy, childhood and puberty, may be the windows of highest vulnerability to damage from BPA exposure.
  • Very few studies have examined the health effects of BPA in humans.  

CERCH Findings on BPA:

- Maternal Urinary Bisphenol A During Pregnancy and Maternal and Neonatal Thyroid Function in theCHAMACOS Study

  • Results suggest that exposure to BPA during pregnancy is related to reduced total T4 in pregnant women and decreased TSH in male neonates.
  • Findings may have implications for fetal and neonatal development.

- Maternal Bisphenol A Exposure During Pregnancy and its Association with Adipokines in Mexican-American Children

  • BPA concentrations during late pregnancy were associated with increased plasma leptin in boys
  • BPA concentrations during early pregnancy are directly associated with plasma adiponectin levels in girls 

-Prenatal and Postnatal Bisphenol A Exposure and Body Mass Index in Childhood in the CHAMACOS Cohort

  • Higher urinary BPA concentrations at 9 years of age were associated with increased adiposity at 9 years
  • Increasing BPA concentrations in mothers during pregnancy were associated with decreased BMI, body fat, and overweight/obesity among their daughters at 9 years of age.

Flame Retardants- Polybrominated Diphenyl Ethers (PBDEs) 

Used to reduce the flammability of in-home items, including textiles, foam in furniture,  carpet padding, and plastic casing for electronics. Also used in construction materials,  automobiles and airplanes.

 TV and Armchair

How are we exposed to PBDEs?

  • PBDEs are not chemically bound to products that contain them and can leach into the surrounding environment where they may remain for years, especially indoors.
  • PBDEs have been found across the globe in air, soil, sediment, dust, food,  wildlife, and humans.
  • House dust is thought to be one of the main pathways for human exposure to PBDEs.

Why are we concerned about PBDEs?

  • Detectable in the blood of 97% of US adults. Globally, most people have measurable levels of PBDEs in their bodies. Higher levels have been observed in North Americans than Europeans or Asians. 
  • Linked to hormonal and neurodevelopmental disruption in both human and animal studies.
  • Have a similar structure to thyroid hormones and can alter their function, potentially interfering with fetal and child brain development.
  • Have been found in human breast milk, potentially exposing young children to toxic disruption.

What is being done?

  • Growing concerns about the health impacts of PBDEs have led to decline in their production and bans on their use in the U.S., Europe and other countries.
  • However, it is likely that exposures to PBDEs will continue for a long period because many items currently in our homes were manufactured before new regulations. 

CERCH Findings on PBDEs:

- The CHAMACOS Study: Health Outcomes Study

Higher PBDE exposures during pregnancy were associated with:

  • Decreased female fertility. 
  • Altered maternal, but not neonatal,  thyroid hormone levels during pregnancy.
  • Lower infant birth weight.