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EPA-Expo-Box (A Toolbox for Exposure Assessors)

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Phthalates and Bisphenol A (BPA)

Phthalates contain a phenyl ring with two attached and extended acetate groups. Many of these compounds are liquids used to make plastics more flexible and resilient, called plasticizers. Low-molecular-weight phthalates (e.g., DMP, DEP, DBP, DIPB) may be found in some personal-hygiene and cosmetic products (NRC, 2008). High- molecular-weight phthalates (e.g., DEHP, DOP, and DINP) are used in plastic tubing, food packaging and processing materials, containers, vinyl toys, vinyl floor coverings, and building products. Di(2-ethylhexyl) phthalate (DEHP) is the most widely used phthalate.

Bisphenol A (BPA), while not a phthalate, is similar to phthalates in that it is mainly used to make polycarbonate plastic and epoxy resins, and is used in food and beverage packaging. BPA is also used in thermal printing applications such as cash register receipts as a chemical dye developer. While the major use of this high production volume chemical is polycarbonate plastics and expoxy resins, its use in food packaging and receipts represent significant human exposure routes (U.S. EPA, 2012).

Example Phthalate and BPA Structures
General Phthalate Structure
General Phthalate Structure
Bis(2-ethylhexyl)phthalate (DEHP)
DEHP
Bisphenol A (BPA)
BPA

Physicochemical Properties

The table below provides a summary of key physicochemical factors that are likely to affect partitioning and fate of select phthalates in the environment. For chemical-specific values, consult the resources provided in the introduction to this module.

Property Fate and Transport Implications
Vapor pressure at 25°C (atm)

Low volatility of most phthalates means that they are not likely to move from water to air, residence time in air is limited. Low volatility is exploited by uses of phthalates in plastic products intended for high-heat conditions, however, phthalates have been shown to volatilize at appreciable amounts from products such as paints, upholstery, and flooring, because of the high surface-area-to-volume ratio of these uses.

Henry’s Law Constant

Phthalates have low Henry’s Law Constants, which correspond with their low vapor pressures and implies a tendency to favor partitioning to water over air. Henry’s Law Constant increases with increased size of the phthalate alkyl chain length, implying that larger molecular weight phthalates have a higher evaporative potential.

Solubility in water (mg/L)

Phthalates have low water solubility, however, phthalates are so widely used that even with low solubility they can be detected at significant concentrations in urban runoff, surface water, and drinking water.

Octanol-Water Partition Coefficient (log value)

High Kow values imply that phthalates are hydrophobic, and preferentially partition to biota, soils, or sediments as opposed to remaining in the water column. This implies likelihood to bioaccumulate and biomagnify in animals and humans. Kow increases with increasing alkyl chain length, meaning larger phthalates are more hydrophobic.

Octanol-Air Partition Coefficient (log value)

High Koa values imply that phthalates are likely to sorb to dust or other particles in the air and settle, rather than remain in a volatile state.

Summary: Phthalates are more likely to be found in water or soil than in air. Phthalates that are released into the air or volatilized will sorb to particles and settle into dust; similarly phthalates released into water are likely to sorb to organic matter or bioaccumulate in biota. Larger-chained phthalates have lower solubility in air and water than the shorter-chained phthalates. Despite this, phthalates can still be measured in air because the use patterns result in high levels of release to air.

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Routes

Humans may be exposed to phthalates via ingestion, inhalation, and dermal contact for their whole lifetime, including in utero (Latini, 2005).

BPA exposure can occur through direct contact with products that use BPA, such as plastics, receipts, or other thermal papers. Residual BPA may be found in recycled paper products due to recycling of thermal papers. BPA may also be found in foods. Canned foods can become contaminated with BPA because it is used in the can lining. BPA can also leach from plastic containers into food or drink, especially if microwaved or if the plastic has been degraded by high heat.

The Routes Tool Set of EPA-Expo-Box provides additional information and resources organized by route.

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Media

Phthalates and BPA may occur as contaminants in most environmental media. The Media Tool Set of EPA-Expo-Box provides additional information and resources organized by media.

Media Sources of Phthalates and BPA
Air
  • Phthalates can be found in indoor air. Certain phthalates volatilize from drying paints or off-gassing from products like new carpets.
  • Phthalates that are released to outdoor air can sorb to dust particles and travel far distances before settling to soil.
  • BPA has been found in air around the world. Burning plastics is presumed to be the source of BPA contamination.
Water
  • Phthalates have been measured in surface water and drinking water. Many liquid soaps, shampoos, and body washes contain phthalates, resulting in high amounts of phthalates entering the waste water streams.
  • BPA is used in many plastic bottles and food containers. BPA can leach from these products when they are washed, entering the waste water stream.
Soil
  • Phthalates sorbed to dust particles can settle and become integrated into soil matrices.
  • Plastic products that are landfilled can result in phthalates and BPA release to soil.
Food
  • Canned foods can become contaminated with BPA because it can leach from the can lining. BPA can also leach from plastic containers into food or drink, especially if microwaved or if the plastic has been degraded by high heat. Some coffee makers contain BPA in the plastic tubes and water containers, and the heat of brewing the coffee can cause migration of the BPA from the plastic into the coffee.
  • Phthalates are present in soft plastic food wrapping. Microwaving foods covered in plastic wrap can result in leaching of the phthalates into the food.
Consumer Products
  • BPA and phthalates are ubiquitous components of consumer products, including personal care products and plastics. Heat and abrasion can accelerate leaching of the compounds from the product matrix.

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Exposed Populations

Phthalates and BPA are ubiquitous in consumer and household products, as they are used in personal care products and many types of plastics. Therefore, the general population may be exposed to phthalates and BPA through a number of different scenarios.

  • Exposures to phthalates can occur through the use of some medications or medical devices (Wittassek et al., 2011). This exposed population may be of particular concern depending on the medical conditions for which they are using the phthalate-containing devices or taking the phthalate-containing medications.
  • Additionally, some research has shown that women have higher phthalate exposure than men, due to the number of personal care products (soaps, shampoos, lotions, cosmetics) that contain phthalates and the market’s predominance by women (James-Todd et al., 2012).
  • Children may also experience higher exposures than adults, due to the presence of phthalates in plastic children’s toys and bottles and the tendency for children to put items in their mouth more frequently than adults. In fact, many products specifically intended for children to put in their mouths (i.e., teething toys, pacifiers) are made from soft plastics containing phthalates.
  • Workers in occupations dealing with receipts, such as cashiers and restaurant servers, may have higher exposures to BPA than the general public.

See the Lifestages and Populations Tool Set of EPA-Expo-Box for resources related to particular population groups and lifestages including workers, children, and women of child-bearing age.

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Tools

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Measure of a substance’s volatility, or its propensity to partition to the vapor (gaseous) phase from its condensed phase (i.e., solid or liquid). This can be used to predict whether inhalation or other exposure routes are more relevant.

Related to Vapor Pressure. Reflects chemical partitioning between the aqueous, dissolved phase and the gaseous phase.

Measure of a substance’s partitioning between dissolved and insoluble phases. Depends on the solute (e.g., water, alcohol) and other substances dissolved in the solute.

Measure of a substance’s partitioning between dissolved and insoluble phases. Depends on the solute (e.g., water, alcohol) and other substances dissolved in the solute.

Ratio of a chemical that has reached equilibrium in adjacent fractions of octanol and water. This ratio is used frequently to estimate how an organic chemical will partition in the environment (e.g., between dissolved and sorbed fractions in surface water) as well as how it will behave in with respect to human tissues. A compound with a high octanol-water partition coefficient is more likely to bioaccumulate in human tissues, especially fatty tissues.

Ratio of a chemical that has reached equilibrium in adjacent fractions of octanol and air. This ratio is used frequently to estimate how an organic chemical will partition in the environment (e.g., between gaseous and particulate fractions in the atmosphere, between soil organic matter and air) as well as how it will behave with respect to human respiratory tissues. A compound with a high octanol-air partition coefficient is more likely to bioaccumulate in human respiratory tissues, particularly is the log octanol-water partition coefficient moderate.

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