After Horrific October Fires, Santa Rosa Water Contaminated By Benzene From Melted Pipes

[hatrack]

Oops.

When a wildfire leveled a whole neighborhood in Santa Rosa, California, in October, it was just the first disaster for this Wine Country city. A second disaster is now unfolding after chemical contamination was detected in the city’s drinking water following the fire.

The Tubbs Fire, part of a trio of fires known as the Central LNU Complex, destroyed more than 5,600 structures and killed 23 people. The first neighborhood it hit was Fountaingrove, an enclave of expensive homes strung along scenic ridgetops. More than 300 homes in the neighborhood burned to the ground.

Soon afterward, some Santa Rosa residents began to smell chemicals in their drinking water. City officials tested some 2,000 water samples after the fire, and have now concluded the contamination came from plastic water supply pipes that melted in the fire. The primary contaminant is benzene, a petrochemical found in some plastic pipes, particularly those made of HDPE plastic.

Plastic water pipes have come under scrutiny in recent decades amid concerns that harmful chemicals may leach from some kinds of pipe. Santa Rosa’s problem, however, is the first known case of plastic pipes causing widespread water contamination after a fire.

EDIT

https://www.newsdeeply.com/water/articles/2018/04/03/after-deadly-wildfire-a-new-problem-for-santa-rosa-contaminated-water

[NNadir]

1. There is a fair amount of poor science reporting in this article.

Polyethylene is not, in general, a plastic "containing benzene." It's an ethylene polymer. This is CH2=CH2. Benzene is C6H6.

Polymers do contain very small amounts of things like initiators and cross linking agents which may be and often are aromatics, but they are generally not "benzene" itself.

Now, it is highly possible, and well known, that the thermolysis of polymers can and do give aromatic compounds, and this may well have happened.

But again, the science reporting here is poor.

It is not the case that metal pipes are necessarily safer than plastic pipes, by the way. Evidence of this fact may be observed in places like, say, Flint Michigan and in many other places.

It is not possible to make any technological object that is risk free; however relative risks are worth evaluating.

[hunter]

2. The mass of ABS pipe in California housing is considerably larger.

I don't think HDPE pipe has made significant inroads in the Santa Rosa housing market other than drip irrigation and deeply buried supply lines. Most buyers of expensive housing still insist on copper piping inside their homes.

Drain pipes, however, are ABS, approaching 100% in modern California housing. Plenty of ABS is used for other purposes too.



https://en.wikipedia.org/wiki/Acrylonitrile_butadiene_styrene

There's your benzene.

Burned automobile tires would be another source.

The copper pipe lobby is generally full of shit.

For anyone who believes that everyone on earth deserves indoor plumbing, the copper industry will never be able to meet that demand.

[NNadir]

3. I'm not really familiar with the types of polymers used in California drain pipes.

This said, styrene is not benzene. They have similar properties but benzene is far more toxic in general.

A styrene component is not essential for the generation of benzene. It appears to help, and do so significantly but it is hardly essential. A paper I came across a few years back indicates that pyrolysis of various species of plastic, albeit in the presence of zeolite catalysts, producing significant yields of benzene. The paper is this one: Thermal Degradation of Real-World Waste Plastics and Simulated Mixed Plastics in a Two-Stage Pyrolysis–Catalysis Reactor for Fuel Production (Williams et al, Energy Fuels, 2015, 29 (4), pp 2601–2609)

Depending on temperature, polymers containing nitriles can and do generate hydrogen cyanide, and the fate of nitrogen in pyrrolysis systems is a concern. (At some temperatures, cyanide can be oxidized to less toxic isocyanates and other species - including nitrogen gas and/or nitrous oxide - a matter which requires monitoring of reaction conditions.)

The graphic from the abstract gives a flavor of this degradation:



A relevant excerpt from the text:

The main aromatic compounds produced from catalytic pyrolysis of the plastic samples with zeolite HZSM-5 catalyst shows (Figure 8b) they are mainly single-ring aromatic compounds with benzene, toluene, ethylbenzene, xylenes, and styrene accounting for a significant proportion as reported by others.11,13,26 Benzene is produced in high yield for the pyrolysis−catalysis of the plastic samples, but particularly for PET and for SMP as the catalyst is introduced, while styrene yields are reduced. The reduction of styrene concentration in the presence of a zeolite catalyst has been attributed to the carbenium nature of the acid catalyzed decomposition of polystyrene leading to the formation of aromatic products other than styrene.12 For a simulated mixture of plastics processed at 500 °C, Lopez et al.26 reported toluene concentrations (% peak area) of 8.1% for pyrolysis which increased to 17.5% in the presence of a zeolite ZSM-5 catalyst, ethylbenzene increased from 5.0% to 9.6%, and xylenes increased from <3.0% to 13.8%. Bagri and Williams34 investigated the pyrolysis and pyrolysis− catalysis of polystyrene in a fluidized bed reactor using a zeolite ZSM-5 catalyst. The uncatalyzed pyrolysis oils were found to contain large amounts of styrene. However, the addition of zeolite catalyst resulted in a marked decrease in styrene concentration in the product oils and increased concentrations of mono aromatic compounds. Lin and White35 also reported that the thermal degradation of polystyrene produces high yields of styrene, but catalytic pyrolysis with ZSM-5 catalyst markedly reduced styrene concentration and increased the production of benzene; in addition, ethylbenzene and toluene were also formed at lower concentrations.

Of course this was in the presence of a zeolite catalyst. Zeolites however occur naturally and are, in fact, mined in California. Whether there are any in this region, I am not competent to say.

A building burning at high temperature and stuffed with consumer materials however is likely to offer a number of catalytic sites. It is not clear that the generation of aromatic compounds including but hardly limited to benzene necessarily involves pipes; a typical American home is loaded with plastic materials.

It is worth noting that zeolites are common components of many cosmetic formulations among other things. I would imagine a burning plastic container of certain cosmetic powders would generate significant quantities of aromatics, including but not limited to benzene. They are also widely used in laundry detergents.

Arguably a burned out building is almost always a kind of mini-superfund site, a fact that had some resonance in the case of the terrorist attack on the World Trade Center.

This said, the largest source of benzene exposure in California is undoubtedly motor fuels and the refineries that produce them. The silly "Proposition 65" "warnings" that appear on every gasoline pump in the State reflect an accurate condition. Gasoline is a fairly powerful carcinogen.

The combustion products of buildings, and in fact, biomass and the routine combustion products of dangerous fossil fuels almost always contain toxic compounds; this is why so many people die each year from air pollution, although millions of deaths from air pollution each year, tens of millions every decade, hardly get as much press as the possibility that five or ten people will die from radiation from Fukushima in the next year, and a few hundred in the next half a century.

The reason for this selective attention of course, involves journalists, and the very, very, very, very poor understanding of science by the journalist producing this particular article is yet another demonstration of what I suspect is true: One cannot get a job in journalism if one has passed a college level chemistry course.

Nobody likes wild fires flashing through people's homes of course, but these types of events are clearly related to a changing climate, and the changing climate will result in an ever increasing frequency of such events. We cannot expect them to be non-toxic besides being hot.

Focusing on detectable benzene is water supplies is, in my view, merely a distraction from the greater issue.