Androgen - any male sex hormone, such as testosterone.

Bioaccumulate - the tendency of a substance to be retained by the body. Under the Great Lakes Water Quality Initiative, EPA has classified phthalates as non-bioaccumulating.

Biomagnify - the tendency of a substance to increase in concentration as it proceeds up the food chain from prey to the top consumer. Phthalates do not biomagnify.

Biomonitoring - a direct measure of human exposure to substances. A recent study by the Centers for Disease Control and Prevention (CDC) is an example of biomonitoring; CDC tested human blood and urine samples and found traces of a number of natural and man-made substances.

DINP - Diisononyl phthalate, a general-use vinyl plasticizer. It is the primary plasticizer used in vinyl toys, though it finds many other applications such as garden hoses, shower curtains, vinyl flooring and wall covering.

DIDP - Diisodecyl phthalate, a general-use vinyl plasticizer found in numerous applications such as garden hoses, shower curtains, vinyl flooring and wall covering and sheathing for wiring and cables.

Endocrine disruptor - generally, a substance that interacts with one or more components of the endocrine system to cause adverse effects. There are as yet no fixed definitions or validated tests to characterize endocrine disruptors.

Estrogen - any female sex hormone, such as estradiol.

Estrogen mimic - any non-hormone substance that acts like estrogen, thus preventing the natural estrogen from doing its job. Phthalates are not estrogen mimics.

Exposure - in health matters, a measurement of the level at which one encounters any substance. (See Risk definition).

Hazard - in this context of issues discussed on this web site, the biological effects produced by substances (i.e., toxicity). Hazards pose risks only if the exposure is sufficiently high. (See Risk definition).

Hormones - chemical messengers that are formed in the endocrine glands, such as the adrenal or thyroid gland, and affect the function of organs or tissues designed to receive them.

Metabolism - literally, change. Any process in an organism that produces, changes or breaks down a compound. Digestion is a process of metabolizing the foods taken into the body.

Monomer - a basic building block of a polymer (See Polymer definition).

PBT - a material considered to be persistent in the environment, bioaccumulative, and toxic to fish and wildlife. Phthalates are often improperly referred to as PBTs although they do not have the same characteristics that genuine PBT materials possess (see Bioaccumulation).

Perixosomal proliferation - a biological process that can cause liver changes in rodents and can ultimately lead to liver cancer in those rodents. A rodent dosed with some specific substances (i.e., peroxisome proliferators) manufactures microbodies called perixosomes, which metabolize and neutralize these substances. This takes place in the liver, where most substances are broken down (metabolized). Very high doses of certain phthalates used in rodent tests stimulate the manufacture of peroxisomes in the liver, causing it to enlarge. When the dosing is stopped, the liver returns to normal size. But if the dosing continues for the majority of the rat or mouse's lifetime, the constant stressing of the liver can ultimately cause it to become cancerous. Humans apparently do not have a peroxisome proliferation response like rats, which is a primary reason why cancer experts say liver tumors in rats caused by certain phthalates are not relevant to humans.

Phthalate monoester - In humans, phthalates are partly broken down into their building-block components, and some of these "monoesters" can get into the body from the bloodstream or gut. If ingested, phthalate molecules do not normally get into the body in appreciable quantities.

Polymer - large molecules formed by the chemical combination of at least five monomer units. Proteins, natural rubber, plastics and cellulose are some examples of natural and synthetic polymers. PVC is a polymer of vinyl chloride monomer.

PVC - polyvinyl chloride is a polymer of vinyl chloride monomer. Vinyl chloride monomer is a volatile liquid. PVC is essentially an inert, rigid plastic material.

Reference dose (RfD) - An exposure level defined by the Environmental Protection Agency as "a numerical estimate of a daily oral exposure to the human population, including sensitive subgroups such as children, that is not likely to cause harmful effects during a lifetime."

Risk - the likelihood that exposure to a hazard could cause injury, if the exposure, or dose, is high enough. All substances (including water) produce effects (i.e., toxicity or hazard) but do not pose risk unless the exposures are sufficiently high. The concept is captured in the saying of 16th century Swiss physician Paracelsus and known to every modern doctor and toxicologist: "The dose makes the poison."

Toxicity - the biological effect of a substance. In this context, toxicity and hazard are used interchangeably.

Volatility - the tendency of a material to evaporate. Because of their different molecular sizes, phthalates differ widely in their tendency to evaporate. DEHP, a relatively large molecule used as a plasticizer in vinyl, has much lower volatility than some of the smaller phthalates. As a group of products, phthalates have very low volatility relative to other materials such as solvents. Phthalates do not readily evaporate.


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