. >> reporter: this is in sohern kenya.every morni these girls walk to the water hole 2 1 kilometers away. clean drinking wer is rare in rural kenya. a lot o war's also contaminated, full o insect larvae, bteria and viruses. 2.2 miion people die every year acrosthe world from arrh diarea. these plastic bottles are life insurancfor the families here. the wom fill the tnsparent bottleand place them on the their hu. solar water dinfection. bottles must be exposed to sunlight for at least four hours. >> translator:e've been using thes solar botts for11 ars. the technolo destroys the ger germs. that's h we don't have to boil the water. the wat from soil disinfection tastes better. we don'like the boiled water. reporter: water treated thi way is no long a health risk. ere's a sile proof ohe solar water disinfection. the statistics of a nearby clinic dr. steve is t manager. >> wve had a decrea of bad cases. instead of using the bote in e solar syste of their cleawat. soccording to our records, for the first lee, weot almost 20% de