and newborn head circumference A Greek study from 2014 investigated the link between maternal weight gain during pregnancy, their PCB-exposure level and PCB level in their newborn infants, their birth weight, gestational age, and head circumference. The lower the birth weight and head circumference of the infants was, the higher POP levels during prenatal development had been, but only if mothers had either excessive or inadequate weight gain during pregnancy. No correlation between POP exposure and gestational age was found. A 2013 case-control study conducted 2009 in Indian mothers and their offspring showed prenatal exposure of two types of organochlorine pesticides (HCH, DDT and DDE) impaired the growth of the fetus, reduced the birth weight, length, head circumference and chest circumference. Health effects of PFAS Additive and synergistic effects Evaluation of the effects of POPs on health is very challenging in the laboratory setting. For example, for organisms exposed to a mixture of POPs, the effects are assumed to be additive. Mixtures of POPs can in principle produce synergistic effects. With synergistic effects, the toxicity of each compound is enhanced (or depressed) by the presence of other compounds in the mixture. When put together, the effects can far exceed the approximated additive effects of the POP compound mixture. In urban areas and indoor environments Traditionally it was thought that human exposure to POPs occurred primarily through food, however indoor pollution patterns that characterize certain POPs have challenged this notion. Recent studies of indoor dust and air have implicated indoor environments as a major sources for human exposure via inhalation and ingestion. Furthermore, significant indoor POP pollution must be a major route of human POP exposure, considering the modern trend in spending larger proportions of life indoors. Several studies have shown that indoor (air and dust) POP levels to exceed outdoor (air and soil) POP concentrations. In rainwater In cosmetics and personal care products Per- and polyfluoroalkyl substances (PFAS) are a class of about 9,000 synthetic organofluorine compounds that have multiple highly toxic fluorine atoms attached to an alkyl chain. PFAS are used in the manufacture of a wide range of products such as food packaging and clothing. They are also used by major companies of the cosmetics industry in a wide range of cosmetics, including lipstick, eye liner, mascara, foundation, concealer, lip balm, blush, nail polish and other such products. A 2021 study tested 231 makeup and personal care products