Microconstituents /Trace Chemicals

Biosolids and other organic residuals contain traces of chemicals, sometimes called "microconstituents."  Wastewater, from which biosolids are derived, may contain many natural and synthetic chemicals, some of which are toxic in high enough concentrations.  These chemicals come from natural sources, households, businesses, and street drains. 

Since 2000, there has been growing concern about the potential impacts of traces of synthetic chemicals in the environment. This has been driven by the ability of scientists to measure smaller and smaller amounts - parts per billion, parts per trillion, etc.  Wherever scientists have looked - in surface waters, in soils, in mammals, in the arctic – they have found traces. These traces get into the environment directly from homes and businesses and daily activities.

Are traces of synthetic chemicals in biosolids a concern for the environment?  

NEBRA has long tracked this issue, to continually improve our understanding of the biosolids and residuals products we manage.  So far, researchers have found some impacts of certain trace chemicals - pharmaceuticals, for example – to aquatic organisms living downstream of wastewater treatment facilities. 

But there have been no significant detrimental effects shown from normal biosolids applications to soils in full-scale, field studies using actual biosolids.  This is likely due to the fact that healthy soils are biologically active media that break down and/or sequester trace synthetic chemicals, reducing the potential exposure of biological organisms.

Human exposures and human health risks from microconstituents in biosolids and other residuals are likely lower than the much higher levels experienced in daily use of these chemicals. The fact is, not many people are directly exposed to biosolids. On the other hand, many of the trace chemicals people mention in biosolids are in regular use in homes and businesses; that is where human exposure occurs.

The potential risks from microconstituents in biosolids to soil biota and other environmental receptors have not been studied as much, but also appear to be low.  And it makes sense for research to continue.

In the meantime, it is worth noting that soils, biosolids, and the treatments biosolids go through are effective at reducing concentrations of most microconstituents.  Biosolids recycling to soils can be a solution in dealing with such chemicals, helping remove them from aquatic systems and destroying or sequestering them, as noted in this 2014 presentation, which provides advice on what biosolids managers can do to mitigate potential concerns, even as scientific understanding continues to improve.

Leading research scientists continue to discuss this topic....

See...

The NEBRA office has additional information, references, and referrals.

Microconstituents include chemicals in pharmaceuticals & personal care products (PPCPs).

Microconstituents include chemicals in pharmaceuticals & personal care products (PPCPs).

You can help protect biosolids quality. Toilets & drains are not trash cans. Learn more...

You can help protect biosolids quality. Toilets & drains are not trash cans. Learn more...

One way to assess impacts of the mixture of chemicals that are biosolids & residuals is with bioassays.  Learn more... (photo courtesy of Puddephat/ McCarthy, Ryerson Univ.)

One way to assess impacts of the mixture of chemicals that are biosolids & residuals is with bioassaysLearn more... (photo courtesy of Puddephat/ McCarthy, Ryerson Univ.)