Can Toxicokinetic and Toxicodynamic Modeling Be Used to Understand and Predict Synergistic Interactions between Chemicals?

Nina Cedergreen, Kristoffer Dalhoff, Dan Li, Michele Gottardi, and Andreas C. Kretschmann (2017). “Can Toxicokinetic and Toxicodynamic Modeling Be Used to Understand and Predict Synergistic Interactions between Chemicals?” Environmental Science & Technology Article ASAP
DOI: 10.1021/acs.est.7b02723

Abstract: Some chemicals are known to enhance the effect of other chemicals beyond what can be predicted with standard mixture models, such as concentration addition and independent action. These chemicals are called synergists. Up until now, no models exist that can predict the joint effect of mixtures including synergists. The aim of the present study is to develop a mechanistic toxicokinetic (TK) and toxicodynamic (TD) model for the synergistic mixture of the azole fungicide, propiconazole (the synergist), and the insecticide, α-cypermethrin, on the mortality of the crustacean Daphnia magna. The study tests the hypothesis that the mechanism of synergy is the azole decreasing the biotransformation rate of α-cypermethrin and validates the predictive ability of the model on another azole with a different potency: prochloraz. The study showed that the synergistic potential of azoles could be explained by their effect on the biotransformation rate but that this effect could only partly be explained by the effect of the two azoles on cytochrome P450 activity, measured on D. magna in vivo. TKTD models of interacting mixtures seem to be a promising tool to test mechanisms of interactions between chemicals. Their predictive ability is, however, still uncertain.

Children’s Safe Products Reporting Rule: Chemicals of High Concern to Children Added or Delisted during the 2017 Rule Update

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Twenty-two chemicals are added as Chemicals of High Concern to Children in the adopted CSPA Reporting Rule (Washington State). The evaluations completed by Ecology and Health are provided in this document. Each evaluation includes the CAS number, a common chemical name, summary of toxicity, summary of potential for exposure, and a list of references. Some CHCC evaluations cover more than one chemical.

Exposure to environmental chemicals is an important risk factor for breast cancer

Read the full story from the Silent Spring Institute.

Exposure to environmental chemicals, especially early in life, is an important contributing factor in the development of breast cancer, according to the most comprehensive review of human studies to date. The findings could help inform prevention strategies aimed at reducing the incidence of the disease, as rates continue to increase worldwide.

Did Monsanto ignore evidence linking its weed killer to cancer?

Read the full story from the Food & Environment Reporting Network.

Roundup’s active ingredient, glyphosate, is widely perceived to be innocuous in the environment because it targets an enzyme not found in animals or humans. When it comes to plants, however, the chemical kills indiscriminately—except for those plants genetically designed to withstand it. In the 1990s, Monsanto began to sell its patented “Roundup Ready” seeds, allowing farmers to spray for weeds without damaging their crops. The combination of herbicide and resistant seeds helped Monsanto become one of the world’s most powerful agriculture corporations. Today, over 90 percent of domestic soy, corn, and cotton crops are genetically engineered to be glyphosate-resistant, accounting for more than 168 million acres.

But the future of the ubiquitous herbicide is in question. Monsanto is currently fighting allegations that glyphosate might not be as safe as advertised, particularly when combined with other chemicals in Roundup. In 2015, an international science committee ruled that glyphosate is a probable human carcinogen, countering previous determinations by regulatory agencies in the United States and other countries. Soon after, more than 200 people sued Monsanto in a federal case now centralized in California, claiming that Roundup caused them to develop non-Hodgkin’s lymphoma, a common blood cancer. Over 1,000 people have filed similar suits against the company in state courts in Arizona, Delaware, Missouri, Nebraska, and elsewhere.

The School Synthetic-Turf Wars

Read the full story in The Atlantic.

More than 8,000 artificial-turf surfaces are currently in use across America, from youth sports fields to professional stadiums, according to the Synthetic Turf Council. The fields are durable, rain-resistant, and low-maintenance, and their sleek designs appeal to young athletes and their parents. But in recent years, some researchers have raised concerns about the safety of these surfaces and their infills, which are typically made from scrap tires…

The Energy 202: The other scientific consensus the EPA is bucking

Read the full story in the Washington Post.

The Trump administration skepticism of climate-change science is no secret.

But there’s another scientific consensus the Environmental Protection Agency just bucked on Tuesday when it announced it is unraveling the Obama administration’s effort to reduce carbon dioxide emissions from the nation’s electricity sector known as the Clean Power Plan.

That would be the scientific agreement that there is no safe level of coal-fired power plant pollution that is healthy to breathe.

Seal Meat, Gold Mining: How Lower-Income Women Are Exposed To Mercury

Read the full story from NPR.

Most people have had some exposure to mercury. Fish is one source. So are mercury vapors from workplaces and factories. That’s what the World Health Organization and the Centers for Disease Control and Prevention say.

At very low levels, the mercury isn’t likely a problem (although it’s hard to say exactly how low is “safe.”)

But higher levels can cause damage to the kidney, lungs and neurological systems. And for women of childbearing age there’s a severe additional risk: mercury levels that exceed the Environmental Protection Agency’s “reference dose” — the level of daily exposure that the EPA says is unlikely to negatively affect people’s health — could damage the fetus that a pregnant woman is carrying, including its kidneys, cardiovascular system and IQ.

And how many women are potentially at risk? That was the question behind a new report: “Mercury in Women of Childbearing Age in 25 Countries,” from IPEN, a nonprofit devoted to issues of global health and toxic chemicals, and Biodiversity Research Institute, an ecology research organization. The groups studied 1,044 women from lower-income countries and found that 42 percent had average mercury levels exceeding the EPA reference dose in their hair samples.