NTP Weighing Glyphosate, Pesticide Formulation Studies

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By Pat Rizzuto

June 15 — The National Toxicology Program may study the cancer and other hazards of glyphosate compared with products that combine it with other ingredients, according to a presentation an NTP scientist made June 15.

Glyphosate, which is sold under brand names including Roundup®, Extreme® Herbicide and Rage™ Herbicide, is the active ingredient in pesticide products registered by many companies, including the BASF Corp., DuPont, Monsanto, FMC Corp., and Syngenta Crop Protection LLC., according to information from the National Pesticide Information Retrieval System, which combines federal and state information.

Glyphosate is the most heavily used herbicide in the U.S. and the world, NTP toxicologist Stephanie Smith-Roe told the program's Board of Scientific Counselors June 15.

She spoke during a portion of the board meeting designed to offer NTP insight and advice about research it could undertake on glyphosate, synthetic turf and crumb rubber and thallium.

Research and regulatory institutions around the world have reached divergent conclusions about glyphosate's carcinogenicity, she said.

The regulatory agencies, however, have focused solely on glyphosate, while some research suggests chemicals in formulations of glyphosate-containing products may be key contributors to toxicity, Smith-Roe said.

NTP research could inform this global discussion by conducting rapid screening tests and short-term laboratory animal experiments that would explore questions such as whether chemicals other than glyphosate that are included in pesticide formulations cause animal toxicity, she said.

NTP's research also could look at ways glyphosate affects the body other than cancer, Smith-Roe said.

Public, Regulatory Interest

George Corcoran, a Wayne State University professor and member of NTP's board, said there would be great public and regulatory interest in the proposed research in light of the pesticide's widespread global usage and divergent scientific assessments about it.

There are so many different mixtures of glyphosate products available, however, that he questioned whether NTP's research would clarify public health questions arising about the pesticide. Corcoran was the only board member who commented on the merits of NTP's possible research.

More then 1.7 million tons of glyphosate were used in the U.S. between 1974 and 2014, while more than 9.4 million tons were used globally during the same time, Smith-Roe said.

More than 750 products containing glyphosate are available in the U.S. alone, she said.

Glyphosate Studies

In 2015, the World Health Organization's International Agency for Research on Cancer (IARC) concluded glyphosate is “probably carcinogenic to humans.”

IARC's classification contrasts with conclusions the European Food Safety Agency and the Joint Food and Agriculture Organization/WHO's Meeting on Pesticide Residues (JMPR) reached in 2015 and 2016, Smith-Roe said.

Those institutions found glyphosate unlikely to pose a cancer risk to people, she said.

The EPA is re-registering the pesticide, she said. Previously the agency had said glyphosate showed “evidence of non-carcinogenicity,” she said.

The different conclusions may arise because IARC conducts only hazard identifications, in which a substance's capacity to be carcinogenic is examined, she said.

The European Food Safety Agency, JMPR and the EPA, however, look at risks, which includes the hazard of a substance and exposure to it, Smith-Roe said.

All three agencies also had access to many unpublished studies that companies submitted to register their pesticides, she said.

Goals of NTP Research

Smith-Roe described the goals of NTP's possible research as:

  •  comparing the toxicity of glyphosate versus formulations and different formulations to each other;
  •  providing publicly available data on cancer and non-cancer health concerns; and
  •  investigating biological mechanisms that could help explain how glyphosate and formulations cause toxicity.


NTP will discuss with other federal and state agencies the value of proceeding with the glyphosate research compared to other possible studies it discussed for thallium and synthetic turf and crumb rubber and other research the program is considering.

Crumb Rubber, Synthetic Turf

NTP is exploring the feasibility of conducting short-term studies of crumb rubber or chemicals in the rubber and shredded bits of recycled tires that separate plastic fiber “grass” on synthetic turf.

More than 11,000 synthetic turf fields exist in the U.S., and about 1,200 are added each year, according to information NTP posted prior to the meeting.

Athletes, including schoolchildren, may ingest the crumbs of rubber as they fall while playing or be exposed through skinned knees or other parts of the body.

Some studies have suggested soccer players, particularly women, are contracting blood cancers due to their exposures.

Board members voiced strong interest in the general topic but urged NTP to focus on research that could identify the specific chemicals that are released by the crumb rubber.

To contact the reporter on this story: Pat Rizzuto in Washington at prizzuto@bna.com

To contact the editor responsible for this story: Larry Pearl at lpearl@bna.com

For More Information

Materials NTP discussed at its board meeting and public comments submitted to the board are available at http://1.usa.gov/1Q5NagL.