Despite several decades of study, ambiguities persist in terms used to express environmental and biotic occurrences of polychlorinated alkanes (PCAs), the main ingredient of chlorinated paraffins (CPs). This can lead to misinterpretation of data between analytical chemists, toxicologists, risk assessors/managers and regulators. The terms recommended here to harmonise reporting and reduce ambiguity use the conventional definition of PCAs linear chlorinated alkanes (typically, C->= 10) with one chlorine per carbon, although some evidence of multiple chlorination exists. Other recommendations include.reporting the "Sum of measured PCAs" because "Total PCAs" is currently unquantifiable.reporting individual chain lengths, e.g., Sigma PCAs-C-11, Sigma PCAs-C-13, allows easier comparability and allows toxicology and risk assessment to consider different PCA combinations.maintain studies on individual PCAs in order to better characterise chemical, environmental and health risk behaviour.The terms could be extended in future to assimilate new findings on individual PCAs, multiple chlorination and chirality.