Jouji Hirai, a former member of the Chiba Prefectural Assembly, and eight others were arrested Monday for allegedly dumping sand that contained industrial waste in a fill site off Chiba Prefecture.
Hirai, 72, president of transport firm Kyoei Transportation, denied the charge.
"One of our clients mixed a few hundred truckloads worth of (industrial waste) into the sand, so the incident has nothing to do with us," he said.
But police allege Hirai and the others transported the sand with the knowledge it contained industrial waste.