4.1 Regulations, standards, and market-defined requirements for chemical constituent ("substances of interest") compliance and conformance have become increasing numerous and complex. Specific laws and standards may pertain to certain product and industry segments, for example, electrical/electronic instruments and components, pharmaceuticals, medical devices, consumer products, agrichemicals, and so forth. Others may be broader and relate specifically to assessment and management of specific chemical compounds or classes across multiple product sectors and sources, for example Ref (2). In addition, such requirements may be issued by national authorities, international standards setting groups, or, in the case of market-defined requirements, even by customer advocacy organizations or customers through supply contracts. The resulting global landscape of requirements and market access expectations is complex, and compliance/conformance presents numerous challenges for manufacturers.

Note 1: For example, IEC 62474:2012 provides some standardized definitions for reporting thresholds and declaration statements for electrotechnical industry. In another example, ISO 14021:2016 addresses self-declared environmental claims.

4.2 Declarable substances may be found on various lists and forms, including those listed in Refs (2-10) and on supply agreements and questionnaires. This guide is not intended to be exhaustive nor cover all declarable substances. Nor does this guide address specific declaration and labeling requirements within these regulation and standards nor address product safety and compliance requirements as dictated by law for specific products, industries, or market regions.

4.3 In addition to new laws and standards, more chemical substances are continually added to a variety of screening lists for review of potential hazards, identification and quantification of possible health or environmental hazards, or both, and consideration of control measures. To comply with these requirements, significant efforts are being directed to detailed data gathering throughout manufacturer supply chains, documentation of presence or absence of such declarable substances, and continual "update" maintenance of the resultant information. Standardized processes have been proposed to assess the potential for a material to contain a possible substance of interest/concern.

4.4 Because of requirements being placed on concentrations of declarable substances within (or on) materials, assessing conformance of products has become a complex, time-consuming, and expensive task. This guide is intended to assist the user in developing a protocol for product assessment. This guide is also directed toward interpretation and communication of the resultant information, specifically where clear objective/numeric data are not available or obtainable, and in the absence of directly applicable regulatory direction. This guide is intended to harmonize language used to interpret and communicate results of these formulation-based or direct-analysis based assessments. Examples include "not expected to contain," "not intentionally added," "not used in formulation," "below de minimis levels," "below analytical detection limits," "not toxicologically significant," "not material to safety," "free of," and so forth.

4.5 A priori knowledge is based on logical deduction and scientific principles, so actual testing of a material may not be required to assess conformance to requirements. For example, it is possible to deduce that organic substances will not survive the temperatures required to produce wrought steel, so there is no need to test for organic substances in wrought steel nor is it possible to develop test methods and reference materials for determination of organic substances within wrought steel.

4.6 A posteriori knowledge is based on observation, experience and known facts. If a priori knowledge cannot rule out the possibility that a substance is present within (or on) a material, a test method may be required to verify or generate information on the concentration of that substance within (or on) the material.

4.7 Statements provided by a manufacturer about declarable substances in a product may contain either or both a priori and a posteriori information. The recipient of such statements may be downstream manufacturers who incorporate multiple materials and components into other products with their own subsequent documentation on declarable substances. Each producer is responsible for its own products' substance declarations, including any potential inaccuracies that may be provided by suppliers. Thus, each manufacturer should take into account its suppliers' risk profiles when choosing to rely on supplier declarations.

4.8 Test methods can be used to verify and provide information related to substances within materials. At the same time, misinformation can be generated or inappropriate conclusions drawn when test methods are misapplied. This guide is intended to provide recommendations on the application of test methods.

4.9 Test methods may be applied by producers or by interim or end users of materials. However, it is not necessary or cost effective to test materials at each stage of production. The decision to apply test methods and the frequency of testing should be based on risk perceived by the user or can be a matter of agreement.

4.10 Assessment of different types and classes of materials each have their individual complexities and nuances given the advancements in both materials and analytical evaluation methods.

4.11 For some regulations and directives, a clear de minimis threshold has been defined for a substance or group of substances. In the absence of a prescribed de minimis, 0.1 % (w/w) is a suitable threshold.

4.11.1 The de minimis level may be described as an individual limit, or as an aggregated limit, whose details will be dependent on a specific regulation. In no instance shall an aggregated de minimis exceed the sum of the prescribed de minimis for the collective group of substances.

4.12 This guide includes a general process and case studies in order to provide guidance and to distinguish when a priori and a posteriori knowledge should be applied. Flow charts as a guide for assessment of materials and products are provided in Appendix X1.