of abnormal levels of cholesterol. Specifically, epidemiological studies in humans have reported an association between increased PFOS levels and the total cholesterol and low density lipoprotein (LDL) cholesterol. ADHD Levels of PFOS in US children aged 12–15 were associated with an increased risk (60% over the interquartile range) of attention deficit hyperactivity disorder (ADHD). The importance of exposure timing during development is unclear, however, some evidence has shown that exposure to PFOS during fetal development was not associated with an increased risk for developing of ADHD later in childhood. Chronic kidney disease Serum levels of PFOS were found to be associated with increased risk of chronic kidney disease in the general US population. "This association was independent of confounders such as age, sex, race/ethnicity, body mass index, diabetes, hypertension, and serum cholesterol level." According to a 2002 study by the Environmental Directorate of the OECD, "PFOS is persistent, bioaccumulative, and toxic to mammalian species." Cancer Research demonstrating the association between PFOS and cancer is still ongoing. A few studies have demonstrated an elevated risk for prostate and bladder cancer, however, there were notable limitations in the design and analysis of these studies. PFOA, another long-chain PFAS compound, has been classified as "possibly carcinogenic to humans" (class 2b) by the International Agency for Research on Cancer (IARC) based on evidence demonstrating an association with testicular and kidney cancer. The Division of Cancer Epidemiology & Genetics (DCEG) is currently investigating the association of several PFAS compounds and cancers including kidney cancer, testicular cancer, prostate cancer, ovarian and endometrial cancer, thyroid cancer, non-hodgkins lymphoma, and childhood leukemia. In wildlife The levels observed in wild animals are considered sufficient to "alter health parameters". PFOS affects the immune system of male mice at a blood serum concentration of 91.5 parts per billion, raising the possibility that highly exposed people and wildlife are immunocompromised. Chicken eggs dosed at 1 milligram per kilogram (or 1 part per million) of egg weight developed into juvenile chickens with an average of ~150 parts per billion in blood serum—and showed brain asymmetry and decreased immunoglobulin levels. Regulation Globally It was added to Annex B of the Stockholm Convention on Persistent Organic Pollutants in May 2009. Originally, parties agreed on acceptable proposes (time-unlimited exemptions) for the following uses—in addition to a range of specific exemptions (time-limited): Photo-imaging Photo-resist and anti-reflective coatings for semi-conductors Etching agent for compound semi-conductors and ceramic filters