<prompt> Translate the following text to EnglishKwa mfano, nitrati huchangia asilimia 20 hadi 40 ya matatizo ya kuona katika mbuga za kitaifa na maeneo ya jangwa katika Kusini mwa California.  <response>: For example, nitrates account for 20-40 percent of visibility impairment in national parks and wilderness areas in Southern California. 