With the growth of hydraulic fracturing in the United States, "public exposure to the many chemicals involved in energy development is expected to increase over the next few years, with uncertain consequences" per science writer Valerie Brown in 2007.
With the growth of hydraulic fracturing in the United States in the following years, concern grew. "Public exposure to the many chemicals involved in energy development is expected to increase over the next few years, with uncertain consequences" wrote science writer Valerie Brown in 2007.