Table 1 shows the included risk factors and their organisation into a hierarchy with three levels. Level 1 risks are clusters of risk factors that are related by mechanism, biology, or potential policy intervention. Most risks are presented at level 2. For occupational carcinogens, a third level is included to provide additional detail about specific carcinogens. For suboptimal breastfeeding we also include a third level to distinguish between nonexclusive breastfeeding during the first 6 months and discontinued breastfeeding from 6 to 23 months.
