Monday, May 24, 2010

Dioxins, triclosan, and chemical management

Skeletal formulas and substituent numbering schemes of dioxin isomers

Dioxin is a general term that describes a group of hundreds of chemicals in the environment, manufactured both by humans and by nature. Dioxins are formed during combustion or burning.  Sources of dioxins include commercial or municipal waste incineration; the burning of fuels like wood, coal, or oil; and natural processes such as forest fires.

"Dioxins" more specifically indicates a group of chemical compounds that share certain chemical structures and biological characteristics. Several hundred of these compounds exist and are members of three closely related families: the chlorinated dibenzo-p-dioxins (CDDs), chlorinated dibenzofurans (CDFs) and certain polychlorinated biphenyls (PCBs).  The Maine EPA site is a good reference.  PCBs are manufactured products no longer produced in the United States.

Know your chemicals

Knowing your chemicals goes a long way towards risk mitigation.  Typically in this blog we speak to manufacturers about chemicals and risk mitigation. Now, obviously, it's a deep consumer concern as well.

Manufacturers keep track of their chemicals, substance-volumes and chemical mixtures using technology like this software package from Actio Corp:

Manufacturers are now installing tools to manage chemical and substance production and waste streams (see above).  How responsible should consumers expect manufacturers to be?  Should every citizen exercise the right to bear a chemical-testing device in their home, to defend home and family?  That's not a bad idea -- but is not a complete, or even feasible, solution.  Being informed is a strong start for everyone.  And while there's a saying, "a little knowledge can be worse than no knowledge at all," think hysteria and misinformation, the public discussion must begin somewhere.

Dioxins in general

The term "dioxin" is commonly used to refer to a family of toxic chemicals that share a similar chemical structure and induce harm through a similar mechanism. Dioxins have been characterized by EPA as likely human carcinogens.  They are anticipated to increase the risk of cancer at background levels of exposure.  Details can be found on the EPA dioxin page.  Nice article recently by Chemical Online

Dioxins - generally - are formed as a result of combustion processes such as commercial or municipal waste incineration and from burning fuels (like wood, coal or oil).  Almost every living creature has been exposed to dioxins (see also G9). Studies have shown that exposure to dioxins at high enough levels may cause a number of adverse health effects.

Health effects?

The most common health effect in people exposed to large amounts of dioxin is skin disease (details here).  Other possible effects include excessive body hair and mild liver damage.  There is some concern that exposure to low levels of dioxins over long periods (or high level exposures at sensitive times) might result in reproductive or developmental effects.  The state of Maine EPA site says, "At extremely low levels, dioxin can alter the way cells grow and develop. Scientists agree that one form of dioxin causes cancer in humans; some chemical forms of dioxin are considered likely to cause cancer."

Notably, the FDA does not recommend personal dioxin testing. Tests for measuring dioxin levels in humans are not routinely available, the FDA says, and laboratories that offer dioxin testing generally do not have the required certification for medical testing. Also: the amount of dioxin in a person’s body is not helpful for predicting or screening disease.

On the FDA Dioxin page, section G12, there is the following question-and-answer:
Q: How can I reduce my personal dioxin levels?
A: eat healthier (!)

Eat less animal fat - because of the high concentrations of dioxins said to be therein - and eat more vegetables and whole grain products. 

Well, haven't we heard that before: eat your vegetables and trim the fat.  Okay, already!  Science and Mom have finally met in the middle.

Dioxins, triclosan, and the Mississippi River

The University of Minnesota study, released this week, examined sediment samples from Lake Pepin, which allowed researchers to analyze the accumulation of pollutants over time. Story is nicely authored by Jon Swedien.  The University Water Resources Center published a report.


Researchers found over the past 50 years dioxins - described by U of M Civil Engineering Professor William Arnold as a "generally nasty (class of) chemicals" - had in all cases decreased, with the exception of those derived from triclosan, an ingredient found in some hand and dish soaps and deodorants.

"These four dioxins only come from triclosan. They didn't exist in Lake Pepin before triclosan was introduced," said Arnold, who supervised the study, in a university press release. Dioxins that end up in the Mississippi by the way of triclosan, an antibacterial agent first added to soaps in 1987, has risen between 200 to 300 percent in recent decades, according to the study.

Just exactly how toxic these four dioxins are or the specific impacts they might have on the environment is not well understood, Arnold said, but because of the nature of the chemicals there is reason to be concerned. 

Help on the way...

Over the past decade, EPA and industry have worked together to dramatically reduce dioxin emissions. It is important to note that dioxin levels in the United States environment have been declining for the last 30 years due to reductions in man-made sources.

Notably: dioxins break down very slowly.  They are extremely persistent compounds.  A large part of the current exposures to dioxins in the United States is due to release of man-made dioxins that occurred decades ago.  And, because some instances of dioxins are manufactured by nature, even if all human-generated dioxins were eliminated, low levels of naturally produced dioxins would remain.  EPA - with other Gov't departments - is currently looking for ways to further reduce dioxin levels entering the environment and to reduce human exposure. *

Notice: EPA draft dioxin reanalysis report avail for 90-day public review and comment period

as stated in the Dioxin Science Plan and announced in an May 21, 2010 Federal Register Notice. During the review period, EPA has will also announce by Federal Register a public teleconference on or about June 24, 2010, and a public panel meeting on July 13-15, 2010.
The deadline for comments is August19, 2010.  More info here.

The Federal Register notes on public comment process are here:

At the request of Administrator Jackson, EPA is in the process of re-assessing the science on the effects of dioxin, a toxic chemical that is emitted by multiple sources, on the public’s health.

Please submit comments in the approved comment submission format.  Comments on the EPA draft dioxin report may be submitted and reviewed using the link. From the site, select Environmental Protection Agency and the keyword EPA-HQ-ORD-2010-0395 (for the docket ID) to comment on this report.

Dioxin report background

In 2003 EPA and other federal agencies developed a set of questions and answers related to dioxins. They have updated them about every year and a half. These materials have again been updated to include more recent information. These questions and answers provide general information on dioxins such as what they are, where they can be found, and major sources of dioxins. They also discuss possible effects of dioxin exposure in humans, include advice about consumption of food that might contain dioxins, and explain the review process for the dioxin reassessment.

* Lurid detail footnote, either fyi or tmi:  Not all dioxin compounds have the same risk. Different dioxin compounds have different toxicities and dioxins are most often found in mixtures rather than as single compounds in the environment. The most toxic forms of dioxin are 2,3,7,8-TCDD and 1,2,3,7,8-Pentachloredibenzodioxin. A method has been established for comparing the toxicity of different types of dioxins to the toxicity of 2,3,7,8-TCDD and 1,2,3,7,8-PeCDD and adding together the toxicity of mixtures of dioxins. This method is called the "Toxicity Equivalence" or TEQ.