Sludge as new sentinel for human health risks

January 16, 2014

Thousands of chemicals serving a variety of human needs flood into sewage treatment plants once their use life has ended. Many belong to a class of chemicals known as CECs (chemicals of emerging concern), which may pose risks to both human and environmental health. 

Arjun Venkatesan, a recent doctorate, and Rolf Halden, professor and director of the Center for Environmental Security at Arizona State University’s Biodesign Institute, have carried out meticulous tracking of many of these chemicals.  portrait of Rolf Halden Download Full Image

In a study appearing today in the Nature Publishing Group journal Scientific Reports, both authors outline a new approach to the identification of potentially harmful, mass-produced chemicals, describing the accumulation in sludge of 123 distinct CECs. 

Ten of the 11 chemicals found in greatest abundance in treated municipal sludge or biosolids were high-production volume chemicals, including flame-retardants, antimicrobials and surfactants. 

The study shows a strong overlap between chemicals found in biological samples taken from the human population and those detected in municipal biosolids. These findings suggest that analysis of sludge may provide a useful surrogate for the assessment of human exposure and bioaccumulation of potentially hazardous substances.

According to Venkatesan, “presence of CECs in sewage suggests that consumers already may get exposed to these chemicals prior to their discharge into sewage, suggesting a need for human biomonitoring and risk assessment of these priority chemicals.”

Prioritizing the thousands of CECs and predicting their behavior has been a daunting challenge. Evaluation is costly, tedious and time-consuming. Further, as the new study emphasizes, laboratory modeling of chemical behavior, including rates of environmental breakdown and potential for bioaccumulation, often deviate significantly from real-world scenarios. 

Conventional chemical screening evaluates the persistence, bioaccumulation and potential toxicity of various chemicals. The method, however, suffers from two shortcomings: the production rates of chemicals in current use are not incorporated into analysis, and the detailed behavior of these chemicals in real-world biological systems – including the human body – is not assessed.

In the current study, a repository of samples from U.S. wastewater treatment plants, created and maintained by Halden at ASU’s Biodesign Institute, was used to conveniently identify CECs, as well as evaluate their potential for bioaccumulation and their ability to withstand degradation processes. The working hypothesis proposes that such treatment plants may act as reliable gauges for monitoring chemical prevalence and bioaccumulation potential relevant to human society and the environment. 

Specifically, chemicals managing to survive primary and secondary treatment in municipal sewage systems display notable resistance to aerobic and anaerobic digestion processes, and are therefore more likely to stubbornly persist in the environment upon their release. 

As Halden notes, post-treatment sludge provides a sink for water-avoiding (hydrophobic) organic compounds. Such sludge is often applied to land, where the persisting hydrophobic chemicals (including polychlorinated biphenyls, PCBs, briominated flame retardants, BFRs and various pharmaceutical and personal care products, including antimicrobial agents) can accumulate in considerable quantity.

The analysis identified a total of 123 chemicals in biosolids. Of these, 17 brominated chemicals were detected in U.S. biosolids for the first time. The most abundant chemicals were surfactants, which occur commonly in detergents, emulsifiers, foaming agents and dispersants. 

After surfactants, pharmaceutical and personal care products were most abundantly detected, followed by BFRs, which commonly occur in plastics, textiles, electronics and household flame-retardants. BFRs often persist and bioaccumulate in the environment, and, under proper conditions, are also capable of transforming into other hazardous chemicals, including brominated dioxins and furans. The study notes that the pathways by which BFRs enter wastewater treatment facilities remain speculative, requiring further investigation

The surfactant and antimicrobial chemicals identified fall into the category of high production volume compounds, produced in annual quantities of over 450,000 kg (1 million pounds). The study notes that the abundance of some chemicals is traceable to specific societal events – for example, the 2001 anthrax scare, which significantly boosted production and consumption of the antibiotic ciprofloxacin. Antibiotic accumulation in the environment is of particular concern, due to a tendency to cause heightened drug resistance in microbial pathogens.  

The study reveals that 91 percent of the 11 most abundant compounds detected in biosolid samples are high production volume chemicals, reinforcing the strong link between the occurrence of hydrophobic chemicals in sludge and their production volume.  

Hydrophobic compounds occurring in the range of parts per trillion are generally of low environmental occurrence or experience significant biodegradability, or both. On the other hand, those chemicals occurring in parts per million quantities are of potential concern, owing to low biodegradability, high usage and the tendency to accumulate in biosolids due to their hydrophobic nature.                                          

When results of the current study were matched against a comprehensive exposure assessment of environmental chemicals conducted by the Center for Disease Control and Prevention, it was observed that roughly 70 percent of chemicals detected in biosolids were also detected in humans. 

Chemical abundance in biosolids appears to be a reliable indicator of current rates of chemical usage, resistance to biodegradation and potential for bioaccumulation. Further, by using biosolids as a pre-screening step, researchers may reduce the thousands of potentially hazardous CEC chemicals in circulation to a manageable number of priority substances most in need of further evaluation. Such a list of chemicals could then be scrutinized with respect to their absorption, distribution, metabolism and excretion, as well as their potential harmfulness to humans and ecosystems.

“With over 85,000 chemicals in daily use in the U.S., it is a daunting task to pinpoint those that need more monitoring, regulation or replacement with safer alternatives,” Halden says. “It turns out that we can use existing infrastructure – our wastewater treatment plants – to take the chemical pulse of the nation, determine chemical inventories and zero in on risky chemicals prone to harm people, prosperity and the planet.” 

Richard Harth

Science writer, Biodesign Institute at ASU


Phoenix commercial real estate in recovery

January 16, 2014

The experts say Phoenix-area commercial real estate is officially in recovery mode, but still short of expansion. A full 100 percent of the real estate brokers participating in a quarterly survey from the W. P. Carey School of Business at Arizona State University agree the Valley’s commercial sector has followed the local housing market into recovery, but the recovery is slow, uneven and likely to remain that way through much of this year.

The participants recently came together for a forum and the survey about progress on apartments, retail, industrial, offices and more. Ninety percent say they don’t think Phoenix-area land prices have reached their peak yet. Meantime, certain areas, such as Scottsdale, central Phoenix and the southeast Valley, are doing much better than others in the commercial market, with progress overall. Mark Stapp Download Full Image

“We’re seeing little bits of improvement in different parts of the Phoenix-area commercial real estate market,” explains one of the forum’s organizers, Mark Stapp, director of the Master of Real Estate Development program at the W. P. Carey School of Business. “While we’re still dealing with fundamental weakness in the national economy, I do expect to see a significant bounce in the local commercial real estate market within the next year as things continue to get better.”

The brokers participating in The Commercial Real Estate Broker Forum come from a variety of sectors, specializations and brokerage houses across the Valley. The event is moderated and partly organized by Pete Bolton, executive vice president and managing director of Newmark Grubb Knight Frank’s Phoenix office. Quarterly reports are available for download at the W. P. Carey School’s website,, under “Commercial Survey.”

Here are some of the Quarter 1, 2014 results:

Where are we in the cycle?
      • 100 percent – Recovery, 0 percent – Expansion, 0 percent – Correction, 0 percent – Maturity, 0 percent Recession
      • (NOTE: Only 87 percent said the area was in recovery in Quarter 4, 2013.)

In what direction is the metro Phoenix market moving?
      • 73 percent – Up, 27 percent – Stationary, 0 percent – Down

Is uncertainty in the federal government affecting the commercial real estate market and hindering our local growth potential?
      • 100 percent – Yes, 0 percent – No

Will the number of people who have stopped working or stopped looking for work affect commercial real estate/industrial/office/retail/multifamily?
      • 40 percent – Not yet, but it will, 30 percent – No, 30 percent – Yes

Have land prices reached their peak?
      • 90 percent – No, 10 percent – Yes

Have homebuilders stopped buying land?
      • 100 percent – No, 0 percent - Yes

Where are apartment rents headed in the next three months?
      • 45 percent – Stationary, 40 percent – Up, 10 percent – Down; 5 percent – No response

Where are office vacancy rates headed in the next three months?
      • 64 percent –Down, 27 percent – Stationary, 9 percent – Up

Where are retail vacancy rates headed in the next three months?
      • 73 percent –Stationary, 18 percent – Down, 9 percent – Up

Is this a landlord or tenant industrial market?
      • 100 percent – Tenant, 0 percent - Landlord

Where are interest rates for commercial loans headed in the next three months?
      • 91 percent – Stationary, 9 percent – Up, 0 percent - Down

Where are investor returns headed in the next three months?
      • 64 percent –Stationary, 18 percent – Up, 18 percent - Down

Those interested in real estate can hear more about how the housing side of the market is doing at an event next weekend. Stapp will be one of the speakers when the W. P. Carey School of Business and The Arizona Republic present “Phoenix Housing Market Explained II” on Jan. 25 at ASU’s Tempe campus. For more information, visit