Metal contamination decrease with new legislation: A decade of metal risk assessment in urban dust

New scientific discoveries for new applications of materials (e.g., metals) lead to extensive industrial use of these materials, which in turn, has significant negative health and environmental impacts. Governments use legislation as a management tool to control the usage of certain materials to lower contamination. This study investigates the level of metal contamination over a period of 12 years to observe the dynamic changes in response to new legislation or industrial improvements. Metals (i.e., Pb, Zn, Co, Cu) associated with urban roadside dust in 21 sites in Riyadh, Saudi Arabia were analyzed during the period of 2001-2013. Three main conclusions were drawn from this study: 1) Phasing out leaded gasoline was an effective tool to control Pb contamination. The average Pb concentration in the city was 37 times higher in 2001 compared to that in 2013. Twenty-nine percent of the investigated sites were at a significant health risk in 2001 compared to none in 2013. 2) The new substitutes of Zn oxides and new limitations of the Zn content in the rubber industry were effective at controlling the Zn contamination in the urban environment. The average Zn concentration of the city was 8 times higher in 2001 compared to that in 2013. Eighty-one percent of the investigated sites in 2001 were considered to be very highly contaminated (CF > 6) compared to none in 2013. 3) The lack of legislation regarding the Co-content in fossil fuels was probably the main reason for the enhancement of the Co contamination in the whole city, with an increase in the average Co concentration similar to 3 times in 2013 compared to that in 2001. Likewise, the health risk index was increased by 3 times from 2001 to 2013. For Cu, the average Cu concentration in 2001 was almost twice that in 2003 and 2013. Legislation has been observe to be an effective management tool for controlling metal contamination.