Central Data Exchange or CDX means EPA's centralized electronic submission receiving system.

Chemical Information Submission System or CISS means EPA's electronic, web-based reporting tool for the completion and submission of data, reports, and other information, or its successors.

Congener means any one particular member of a class of chemical substances. A specific congener is denoted by unique chemical structure, for example 2,3,7,8-tetrachlorodibenzofuran.

Dibenzofuran means any of a family of compounds which has as a nucleus a triple-ring structure consisting of two benzene rings connected through a pair of bridges between the benzene rings. The bridges are a carbon-carbon bridge and a carbon-oxygen-carbon bridge at both substitution positions.

Dibenzo-p-dioxin or dioxin means any of a family of compounds which has as a nucleus a triple-ring structure consisting of two benzene rings connected through a pair of oxygen atoms.

Guidelines means the Midwest Research Institute (MRI) publication Guidelines for the Determination of Polyhalogenated Dioxins and Dibenzofurans in Commercial Products, EPA contract No. 68-02-3938; MRI Project No. 8201-A(41), 1985.

HDD or 2,3,7,8-HDD means any of the dibenzo-p-dioxins totally chlorinated or totally brominated at the following positions on the molecular structure: 2,3,7,8; 1,2,3,7,8; 1,2,3,4,7,8; 1,2,3,6,7,8; 1,2,3,7,8,9; and 1,2,3,4,7,8,9.

HDF or 2,3,7,8-HDF means any of the dibenzofurans totally chlorinated or totally brominated at the following positions on the molecular structure: 2,3,7,8; 1,2,3,7,8; 2,3,4,7,8; 1,2,3,4,7,8; 1,2,3,6,7,8; 1,2,3,7,8,9; 2,3,4,6,7,8; 1,2,3,4,6,7,8; and 1,2,3,4,7,8,9.

Homolog means a group of isomers that have the same degree of halogenation. For example, the homologous class of tetrachlorodibenzo-p-dioxins consists of all dibenzo-p-dioxins containing four chlorine atoms. When the homologous classes discussed in this part are referred to, the following abbreviations for the prefix denoting the number of halogens are used:

HRGC means high resolution gas chromatography.

HRMS means high resolution mass spectrometry.

Level of quantitation or LOQ means the lowest concentration at which HDDs/HDFs can be reproducibly measured in a specific chemical substance within specified confidence limits, as described in this part.

Polybrominated dibenzofurans refers to any member of a class of dibenzofurans with two to eight bromine substituents.

Polybrominated dibenzo-p-dioxin or PBDD means to any member of a class of dibenzo-p-dioxins with two to eight bromine substituents.

Polychlorinated dibenzofuran means any member of a class of dibenzofurans with two to eight chlorine substituents.

Polychlorinated dibenzo-p-dioxin or PCDD means any member of a class of dibenzo-p-dioxins with two to eight chlorine substituents.

Polyhalogenated dibenzofuran or PHDF means any member of a class of dibenzofurans containing two to eight chlorine, bromine, or a combination of chlorine and bromine substituents.

Polyhalogenated dibenzo-p-dioxin or PHDD means any member of a class of dibenzo-p-dioxins containing two to eight chlorine substituents or two to eight bromine substituents.

Positive test result means:

Precursor means a chemical substance which is not contaminated due to the process conditions under which it is manufactured, but because of its molecular structure, and under favorable process conditions, it may cause or aid the formation of HDDs/HDFs in other chemicals in which it is used as a feedstock or intermediate.

QA means quality assurance.

QC means quality control.

Reimbursement period means the period that begins when the data from the last test to be completed under this part for a specific chemical substance listed in § 766.25 is submitted to EPA, and ends after an amount of time equal to that which had been required to develop that data or 5 years, whichever is later.

TSCA means the Toxic Substances Control Act, 15 U.S.C. 2601 et seq.