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IRIS Descriptions of Organs/Systems




Includes heart and blood vessels (including arteries, capillaries, and veins). 


Relating to the skin, which consists of two main layers, the epidermis and dermis. Also includes hair follicles, sweat glands, sebaceous glands, and nails.


A lifestage that includes the period prior to conception (either parent), the prenatal period, and the postnatal period to the time of sexual maturation. Developmental effects may be detected at any point in the lifespan of the organism, and include: (1) death of the developing organism, (2) structural abnormality, (3) altered growth, and (4) functional deficiency. Teratogenicity is generally used to refer to malformations only (i.e., a permanent structural change that may adversely affect survival, development, or function).


Includes the thyroid gland, parathyroid, hypothalamus, pineal gland, adrenal gland, pituitary gland, pancreas (see also Gastrointestinal), thymus (see also Immune), and testis and ovary (see also Reproductive).


Includes mouth/oral cavity (including tongue), esophagus, stomach, pancreas (see also Endocrine), small intestine (including duodenum, jejunum, and ileum), and large intestine (including cecum, colon, rectum, and anus).


Includes blood plasma, red blood cells (erythrocytes), platelets (thrombocytes), and bone marrow (where blood cells are produced). White blood cells (leukocytes) are part of the Hematologic system, but are included under the Immune system because of their role in the body's defense against infectious organisms and foreign substances.


Includes liver, bile duct, and gall bladder.


Includes white blood cells (leukocytes; see also Hematologic), bone marrow, thymus, spleen, and lymphatic system.


Includes muscle, connective tissue (ligaments, tendons, and cartilage), and bones.


Includes the central nervous system (CNS; brain and spinal cord) and peripheral nervous system (PNS; nerves and ganglia that relay information between the CNS and other parts of the body to regulate sensory, motor, and autonomic processes).

Neurotoxicity involves structural or functional changes in the CNS or PNS.  Structural changes include neuroanatomical or histologic alterations. Functional changes include neurochemical alterations (e.g., neurotransmitter levels), neurophysiological alterations (e.g., nerve conduction), or behavioral effects (e.g., learning; sensory function).

Developmental neurotoxicity is neurotoxicity manifest during development, including changes to the growth or organization of CNS or PNS structures, as well as alterations to the appearance or maturation of different nervous system functions (see also Developmental).


Includes all parts of the eyeball (lens, retina, cornea, etc.), the muscles that position the eye, eyelids, lachrymal/lacrimal glands, and, in some non-human species, the Hardarian gland.


Includes effects not associated with a specific organ system, including changes in body weight, decreased survival, and other nonspecific toxicity (e.g., abnormal appearance, changes in clinical chemistry parameters that could not be attributed to an organ system, and increased hemosiderin deposition).

Also includes reference values based on studies that showed no effects at the highest exposure level tested (e.g., a no-observed-adverse-effect level or NOAEL).  In these cases, because an adverse effect was not identified, an affected organ or system could be assigned.


Includes alterations to the male or female reproductive organs, related endocrine system (see also Endocrine), or pregnancy outcomes. Manifestations may include adverse effects on onset of puberty, gamete production and transport, reproductive cycle normality, sexual behavior, fertility, gestation, parturition, lactation, developmental toxicity, premature reproductive senescence, or modification in other functions dependent on the integrity of the reproductive system.

Female reproductive structures include the uterus, endometrium, ovaries, including eggs, follicles, and corpora lutea (see also Endocrine), fallopian tubes, cervix, vagina, and vulva. Also includes mammary gland and breast.

Male reproductive structures include the testes (see also Endocrine), epididymides, and vas deferens (including sperm); scrotum; seminal vesicles; coagulating glands; prostate gland; and penis. Because of the association between reproductive and urinary system structures, particularly in males, the term urogenital (or genitourinary) system is often used.


Includes the nasal passages, pharynx, larynx, trachea, bronchi, and lungs.


Includes the kidneys, ureter, urinary bladder, and urethra.  Also referred to as the excretory or renal system.  Because of the association between reproductive and urinary system structures, particularly in males, the term urogenital (or genitourinary) system is often used.

(1) The effects that serve as the basis for some IRIS toxicity values could be an indicator of toxicity to more than one organ/system. In these cases, EPA may assign an effect to multiple organs/systems most commonly associated with that effect. Therefore, searches using organ/system filters may return a chemical-specific toxicity value under more than one organ/system.

(2) Cancers that arise in tissues that are pervasive throughout the body (e.g., blood vessels, connective tissue, and mesothelium) are included with the organ system where the tumor was located (e.g., lung mesothelioma is located under "Respiratory").