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

Download the document.

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.

One of the oldest climate change experiments has led to a troubling conclusion

Read the full story in the Washington Post.

One of the regular complaints of climate change doubters and skeptics is that scientific projections of a dire future are too heavily based on computer simulations, or models, which — they say — rest on a variety of questionable assumptions.

But a major climate change study published Thursday relied not on models but experimental data — a 26-year record of observations, no less — to reach a conclusion perhaps just as worrying. The research, tracking the emissions of carbon from artificially heated plots of a forest in Massachusetts, reinforces fears about the possibility of a climate change “feedback” involving the planet’s soils, one that could pile on top of and substantially worsen the ongoing warming trend triggered by the burning of fossil fuels.

Some Power Plants Pollute Worse Than Volcanoes

Read the full story in Bloomberg News.

NASA’s Orbiting Carbon Observatory-2 (OCO-2) is the subject of five studies published in the journal Science on Thursday. They provide new details into these critical flows around the world: how shifting patterns in weather-altering tropical Pacific Ocean temperatures—El Nino conditions—can change the pace of the global CO2 rise; where CO2 travels after leaving specific sources, such as metropolitan Los Angeles or a volcano on Vanuatu; and how change in plant photosynthesis—now visible from space—is responding to the increasing amount of carbon that vegetation is sucking out of the air.

EPA makes ‘climate change’ vanish from four-year plan

Read the full story from CNN.

The Environmental Protection Agency has identified its priorities, and climate change is not one of them.

In fact, the phrase “climate change” does not appear in the agency’s draft four-year strategic plan, a 38-page document quietly released for public comment last week.

Just 10 rivers may be to blame for millions of tonnes of ocean plastic

Read the full story in Cosmos.

Just 10 rivers – eight of them in Asia – may be responsible for dumping almost four million tonnes of plastic into the seas every year.

Calculating with the precision the source and amount of plastic trash in the oceans is difficult; estimates tend to cover wide ranges. Previous research has found about one-fifth of total ocean plastic trash comes from marine activities – plastic tossed from fishing boats, ships, drilling platforms and so on – with four-fifths from land.

A paper published in the journal Environmental Science and Technology, by scientists from the Helmholtz Centre for Environmental Research and the Weihenstephan-Triesdorf University of Applied Science, both in Germany, calculates that rivers contribute between 410,000 and four million tonnes a year to oceanic plastic debris, with 88 to 95% coming from only 10.