Relatively few of them have been tested for their health effects on humans. However, of the ones that have, a significant number have been found to be carcinogenic or to cause disease in other ways.
وبالرغم من انه لم يُفحص سوى القليل منها نسبيا لاكتشاف تأثيرها في البشر ،‏ تبين ان عددا كبيرا مما فُحص يسبب السرطان او غيره من الامراض .‏