While the first alarms bells about PCBs in school buildings may have sounded in New England, the echo of that call-to-arms can now be heard on the west coast.   The discovery of PCBs in Malibu California schools and the press coverage that followed, have shattered the myth that PCBs in schools are only found in older east coast buildings.  For those following the Malibu PCB news, it’s hard to deny the drama that only southern California brings to a story; it’s not hard to imagine this  being the basis for a made for TV movie.

What are the facts?

According to a Fact Sheet dated July 27, 2014 by the Santa Monica-Malibu Unified School District (SMMUSD) an evaluation of school building environmental quality was started after three Malibu High School employees were diagnosed with thyroid cancer.  Following consultation with California environmental and health agencies, the district retained Environ, an environmental engineering firm to assess conditions in the Malibu High School and in the Juan Cabrillo Elementary School.

Environ’s evaluation included testing air, surfaces and certain building materials (paint and caulk) for PCBs.  Note that there is no known correlation between PCB exposure and human or animal thyroid cancer.  While PCBs were found throughout the schools, the detected concentrations were in most case well below USEPA regulatory and public health levels.  No air concentrations exceeded EPA recommended levels, although some caulk samples contained PCB concentrations greater than EPA’s 50 ppm regulatory criteria.

On August 14, 2014 the USEPA Region 9 Regional Administrator issued a letter in which he approved of the plans and actions taken by SMMUSD without exception.  The next day the SMMUSD issued a press release which informed the public that the district’s response to PCBs in the schools had won the endorsement of the USEPA.

What was the public reaction?

In 2013, after PCBs were found in the schools, an organization called Malibu Unites began seeking more testing and ultimately the removal of PCBs from the schools.  The group boasts a membership that includes “parents, teachers, community members, celebrity environmentalists, medical professionals, scientists, and environmental organizations working together for healthy, toxin-free schools”.   The presence of “celebrity environmentalists” has drawn a good deal of attention and press coverage to the group.

Here is an excerpt from an August 29, 2014 article published in the Los Angeles Register that helps convey the sense of frustration felt by the more concerned public:

“Unhappy with the school district’s current clean-up plan, Mayor Skylar Peak said he plans to demand further testing of toxic chemicals at the city’s public schools.

“The City of Malibu doesn’t have any control over its public schools because of state law, but council members decided to put the item on the next agenda after more than an hour of public comments from concerned parents during Monday’s City Council meeting.

“At least 24 parents have taken their children out of Malibu public schools because of elevated levels of PCBs – polychlorinated biphenyl – found in at least five classrooms at Malibu High School.  PCBs are found in window caulking, and sometimes the lighting, of structures built from the 1950s until the chemical was banned by the federal government in 1979.

“Parents and Peak want the district to test the source: the caulk.  The district says the classrooms are safe to re-enter.  Currently, the district is relying on “best practices” of cleaning, dust sampling and air sampling to identify PCB levels”.

Also, a notice of intent to sue the district and the EPA pursuant to the Toxic Substances Control Act was served by the Vititoe Law Group and the Public Employees for Environmental Responsibility (PEER) on August 20, 2014.   The notice gives SMMUSD 60 days to remove toxic materials from the schools or face a federal lawsuit.

Is Malibu the tipping point for PCBs in schools?

In his 2000 best-selling book “The Tipping Point”, Malcolm Gladwell explored the process by which some trends achieve great popularity, while others eventually fade.  The issue of PCBs in schools and other buildings has been simmering just below the surface of public awareness for several years, but outside of the small community of regulators, environmental lawyers and technical consultants, the full potential significance of PCBs in schools and other  buildings has not been understood.

For this post I am not offering my own analysis or opinion about the specific circumstances or health risks associated with PCBs in the Malibu schools.  What I am questioning is whether the Malibu PCB situation may draw sufficient public awareness that it becomes the tipping point that triggers an increased national awareness and policy development regarding PCBs in schools. We’ll see.


 At the end of May I posted an article that reviewed the routes of exposure by which people are exposed to PCBs.  After some general discussion, the article focused on the total PCB intake for three elementary school-aged child receptors who attended schools with different indoor air PCB concentrations:

  • A school with a relatively low 100 ng/m3 (nanograms per cubic meter) of PCBs in air;
  •  A second school with 300ng/m3 of PCBs in air (this is the EPA Public Health Level); and
  •  The third school with 400 ng/m3 of PCBs in air, 33% greater than the EPA Public Health Level.

The article calculated a total average daily dose of PCBs for these different student receptors by adding the amount of PCBs they ingested each day from food (this worked out to be 11.8 ug/day, aka micrograms per day), to the amount of PCB they inhaled at school and the amount they inhaled at home.  Recall that there are 1,000 ng in 1.0 ug.  Here is the summary table I ended up with:

Table 3 – Percentage of Daily PCB Exposure from Food and Air

Scenario

% PCBs from Food

%PCBs from Air

Total % PCB Exposure

1 (100ng/m3)

96.6%

3.4%

100%

2 (300ng/m3)

92.6%

7.4%

100%

3 (400ng/m3)

90.8%

9.2%

100%

The article’s conclusions were: 1) for these student receptors the overwhelming majority of their daily PCB dose comes from their diet; and 2) trying to reduce their daily PCB intake by reducing the concentration of PCBs in school air was a poor use of limited school resources because the proportion of the student’s daily PCB dose coming from air was too small to be of consequence.

What Happens When PCB Air Concentrations are even higher?

Let’s say you are growing a little skeptical about the potential health benefit of reducing PCBs in indoor air when the reduction is from 400 to 300 ng/m3.  But, what if the original indoor air PCB concentration is much higher than 400 ng/m3, what if it were 800ng/m3 (new Scenario 4) or 1,600 ng/m3 (new Scenario 5)?  Okay, take a look at Table 4:

Table 4 – Updated Sum of PCB Daily Exposures from Food and Air (in ug)

Scenario

[PCBs]Food

[PCBs]Air

[PCBs]Total

2 (300ng/m3)

11.8

0.94

12.7

3 (400ng/m3)

11.8

1.20

13.0

4 (800ng/m3)

11.8

2.2

14.0

5 (1,600ng/m3)

11.8

4.3

16.1

What I’ve done here is added the average daily dose of PCBs from food to the average daily dose of PCBs from air for our hypothetical elementary school students.  Scenarios 2 and 3 are the same as before, but new Scenarios 4 and 5 incorporate more extreme indoor air concentrations.  Scenario 5 is an unusually extreme indoor air concentration of PCBs.

Table 5 (below) uses the information just presented in Table 4 to identify what percentage of the student’s average daily PCB intake is coming from food and air with the new scenarios 4 and 5.

Table 5 – Percentage of Daily PCB Exposure from Food and Air

Scenario

% PCBs from Food

%PCBs from Air

Total % PCB Exposure

2 (300ng/m3)

92.6%

7.4%

100.0%

3 (400ng/m3)

90.8%

9.2%

100.0%

4 (800ng/m3)

84.0%

16.0%

100.0%

5 (1,600ng/m3)

73.2%

26.8%

100.0%

Table 5 shows that even when elementary school indoor air concentrations reach 1,600 ng/m3, only 27% of an elementary school student’s daily dose of PCBs would be from air (mostly from school air, but some from air at home too).

The Upside of Removing PCBs from Schools

Finally, Table 6 identifies the percentage reduction in average daily student PCB intake that can be achieved by reducing the indoor air concentration to the EPA Public Health Level of 300 ng/m3:

Table 6 – Percent of PCB Exposure Reduction from Reducing Indoor Air Levels

Scenario

% Reduction

2 (300ng/m3)

0.0%

3 (400ng/m3)

2.0%

4 (800ng/m3)

9.3%

5 (1,600ng/m3)

21.1%

A Lot of Pain to Reduce PCB Air Concentrations, but is there Real Gain?

A conclusion that I did not highlight in the earlier article is that bringing indoor air concentrations down from 400 ng/m3 (a level well above the EPA public Health Level) to 300 ng/m3 will reduce a student’s average daily PCB intake by roughly 2%.  From a toxicological standpoint a 2% reduction cannot be expected to have any discernible health benefit, in fact it is almost certainly a difference too small to measure using even advanced methods.

      By reducing an indoor air concentration from 800 ng/m3 to 300 ng/m3 the total dose reduction for an average student would be just under 10%, again this difference in total PCB dose is too small to measure in a student population if the study were to be done.  Just think about the quality control acceptance criteria for PCB analysis (generally results that fall between 70% and 140% of the true value are considered accurate).  It is unlikely that a 10% difference in dose could be reliably detected.

      For scenario 5, the case with 1,600 ng/m3 PCB in air, it is harder to dismiss a potential 21% reduction in PCB dose as inconsequential.  That large a reduction in dose could in-fact be significant from a health perspective if the total dose received were on the “steep portion” of the dose-response curve.  The steep portion of a dose-response curve is the dose range where small changes in dose are most likely to have the biggest effect.  However, in the case of PCBs the steep part of the dose-response curve just begins at doses between 50 to 500 times greater than the doses we have been considering.  In other words, reducing PCB air concentrations in schools, even those as high as 1,600 ng/m3, are unlikely to produce any measurable health benefit because:

  1. The PCB dose received from the average student diet is still much greater than the dose received from air; and
  2. The total average daily dose of PCBs received by average elementary school children is much less than dose needed to produce detectable health effects.

 It is well known that all people have some amount of polychlorinated biphenyls (PCBs) in their body.  Now the total amount of PCBs we have in us is quite small and there is no real evidence that it is doing us any harm.  But, it is still a good question to ask: how did this happen?  Where did those PCBs come from?  More specifically, what types of exposures caused each of us to acquire our own personal cache of PCBs? 

 When you think the question through, you realize there are really just three possibilities:

 1. We were born with them, in other words we received them from our mothers during gestation in her womb;

2. We absorb PCBs that occur in small amounts from our food; and/or

3. We breathe air that contains small amounts of PCBs and retain them in our bodies.

 Which one of these is the best explanation?  Let’s see what we can figure out.  By the way, in the discussion that follows I am focusing on mean (average) consumers of food and breathers of air.  There are certainly people who for portions of their lives may differ significantly from these means, but most of the population will fall close to these values.

 Were we Born with PCBs?

 It was long assumed that a fetus was protected from drugs and other chemicals present in the maternal blood supply by the action of the placenta and its semi-independent circulatory system.  However, the thalidomide disaster proved that assumption to be false.  From human studies we know that the PCB concentration of umbilical cord blood has roughly half the PCB content of maternal blood.  So while the amount of PCB reaching the fetus from the mother is moderated, it is not eliminated.

 Still, we also know that young children generally have low to non-detectable concentrations of PCBs in their blood.  This may reflect a more rapid rate of PCB excretion for children, or it may be that the total body burden of PCBs received from the mother is small.  So while some portion of an adult’s PCB body burden may have been received from her/his mother during fetal development, the role of maternal PCB transfer to her infant appears to be small and transient.

 PCBs from Food

 It has been known for some time that PCBs are present throughout the human food supply.  The concentration of PCBs in food has been declining for decades and currently ranges from 2-6 micrograms of PCBs per kilogram of food (ug/kg) for fruits, vegetables and grains to 10-50+ ug/kg for chicken, meat, oils, butter and fish.

 To estimate the average daily PCB consumption from food, we need to know how much of the different types of food the average person eats, and the average PCB concentration in that food.  To keep things simple, I am assuming 100% of the PCBs ingested with food are absorbed into the body; a reasonable assumption in most cases.

 Using the USDA data on the average American food consumption and a mid-point in the range of PCB concentrations by food type I calculate that the average American consumes about 15.7 micrograms of PCBs per day in their food.  For comparison a person with a vegan diet (consuming no dairy or meat), the total PCB intake from food would be about 8.9 micrograms per day. 

 For the scenarios considered in the following section, I’ve reduced the average American dietary intake by 25% because the receptor in the exposure scenarios is an elementary school child (1,500 calories/day).  This results in a corresponding 25% reduction in PCB intake (11.8 ug/day for regular diet; 6.68 ug/day for a vegan diet).  If you would like to see my spreadsheet for these calcs please send me an email and I will forward them.

 PCBs from Air

 To estimate the average exposure to PCBs in air we need to know the breathing rate for the average elementary school student and the average PCB concentration in the air they breathe.  Table 6-1 of EPA’s Exposure Factor Handbook is a good source of information on breathing rate.  In the interest of simplicity, I am going to use a breathing rate of 12 cubic meters of air per day (m3/day) for the student. 

 This would be low for an adult and about right for a child.   Someone who is physically exerting themselves will have a much higher breathing rate while the activity lasts, but I am more interested in long-term average exposures than in peak short-term exposures.

 PCB background concentrations in outdoor air can be as low as 0.05 ng/m3 in remote areas and as high as 10 ng/m3 in outdoor urban environments (note that ng/m3 means nanograms per cubic meter; also note that 1,000 ng = 1.0 ug) .  Published data on indoor air PCB concentrations in cases where there is no PCB source material in the building is hard to find. 

 For the purpose of this post, I’m considering three theoretical air exposure scenarios:  

1) a student who lives in a home with 20 ng/m3 PCB in air who attends school in a building 32.5 hours/ week, 36 weeks/year with 100ng/m3 PCB;

2) a student who lives in a home with 20 ng/m3 PCBs in air who spends 32.5 hours per week 36 weeks/year in a building with 300 ng/m3; and

3) a student who lives in a home with 20 ng/m3 and who spends 32.5 hours/week, 36 weeks/year in a building with 400 ng/m3 PCBs.

 The indoor air concentration of 300 ng/m3 corresponds to the USEPA Public Health Level for elementary school age children.  The 400 ng/m3 indoor air concentration corresponds to a level 33% greater than the USEPA Public Health Level for elementary school age children.  Once again, if you’d like to see the spreadsheets, send me an email and I will pass them along.  For simplicity I’m assuming these individuals spend no time at all outside.  The following table shows the results.

Table 1 – Exposures to PCBs in Air

Scenario

Annual PCB Air Exposure (ug)

Average Daily PCB Air Exposure (ug)

1

153

0.42

2

343

0.94

3

438

1.20

Total Daily PCB Exposure

The sum the PCB exposures from eating and breathing are shown in Table 2:

Table 2 – Sum of PCB Daily Exposures from Food and Air (in ug)

Scenario

[PCBs]Food

[PCBs]Air

[PCBs]Total

1

11.8

0.42

12.2

2

11.8

0.94

12.7

3

11.8

1.20

13.0

Finally in Table 3 let’s consider what percentage of daily PCB exposure comes from food and what percentage comes from air:

Table 3 – Percentage of Daily PCB Exposure from Food and Air

Scenario

% PCBs from Food

%PCBs from Air

Total % PCB Exposure

1

96.6%

3.4%

100%

2

92.6%

7.4%

100%

3

90.8%

9.2%

100%

From Table 3 it is apparent that the major exposures to PCBs for these student receptors occurs through the diet and only a relatively small proportion is due to inhalation of PCBs in air, unless the air concentrations are significantly greater than 400 ng/m3.  So food appears to be the major route by which people receive their PCB body burden.

Based on this analysis, efforts to reduce human PCB exposure by reducing PCB concentrations in air in a school setting are often fundamentally flawed because the percentage of total PCB dose received through air is not great enough to make a significant difference in total PCB exposure.  Efforts to reduce PCBs in schools through expensive remediation programs can often be particularly misguided during a period of tight educational budgets.

There is an important limitation to this analysis, it only considers indoor air PCB concentrations up to 400 ng/m3.  Now 400 ng/m3 is a concentration well above normal levels, but indoor air concentration can be this high, or even higher, in some situations.  In my next blog post I’ll take a look at PCBs at higher indoor air concentrations.


The PCB regulations (40 CFR 761) were proposed by the USEPA to implement some of the  specific the requirements in the 1976 Toxic Substance Control Act (TSCA).  While only a small part of TSCA, the PCB mandates (Section 6(e)) looms large in the regulatory world.  Yet a closer look at the history of the TSCA reveals that the the PCB program was more an accident of chance rather than a carefully conceived Congressional initiative.  If you want to learn more about how this particular “sausage” was made, then read on.

The Roots of TSCA

President Richard Nixon (possibly the most pro-environmental president since Teddy Roosevelt) first proposed the Toxic Substance Control Act (TSCA) to the 92nd Congress in 1971 .  The President’s Council on Environmental Quality (CEQ) had crafted the initial TSCA bill over the previous year; coincidentally, the same year that the USEPA itself came into being (1970).  In CEQ’s 1971 report titled Toxic Substances, the the Council argued that the government needed additional legal authorities to regulate toxic substances in commerce to meet the larger goal of protecting public health and the environment.  Here is a summary of the CEQ’s principal arguments for the passage of TSCA:

  1. Toxic substances are entering the environment.  Over 9 million chemicals are known with several thousand new ones added each year.  Although many of these are not toxic, the sheer number of them and the evidence of toxic incidents that have already occurred indicate the nature of the problem.
  2. These substances can have severe effects.  The report describes the range of possible toxic effects in general terms that we are all now familiar with.
  3. Existing legal authorities are inadequate.   The report describes the principal environmental legislation as being media based – the then Federal Water Pollution Control Act for waste water, the Clean Air Act for air pollution etc.  CEQ indicated there was a need for legislation that cut across media and focused directly on potential toxic pollutants.

While the US Senate found the arguments for TSCA persuasive, the House of Representatives did not.  As a result, TSCA languished through the 92nd and 93rd Congresses; the House majority believed TSCA placed unreasonable burdens on industry, particularly the chemical industry.  Recall that the period from 1973 to 1975 was one of severe economic recession; there was little national appetite for adding to the regulatory burden on an already depressed industrial sector.

The Resurgence of US Environmentalism

But the 1960s and ’70s were also periods of rapid growth for the environmental movement.  Pressure was increasing for government to play a larger role in protecting human health and the environment; environmental groups were calling on Congress to do more.  Washington was under siege for action on both the economy and the environment. Given the conflicting interests Congress did what it often does best, nothing.  Meanwhile the draft TSCA legislation collected dust.

Kepone and the Environmental Tipping Point

Meanwhile a tragic series of mishaps at a small pesticide manufacturing plant on the banks of the James River in Hopewell, Virginia was about to grab the national spotlight and indirectly become responsible for the passage of TSCA.     Allied Chemical Company (which subsequently became AlliedSignal) had a manufacturing plant in Hopewell that produced a small volume pesticide named Kepone (aka chlordecone).  In 1973 the overseas demand for Kepone began to increase and rather than expanding its own production facilities to meet this demand, Allied leased the Kepone production rights to two of its Hopewell employees.  These employees started a new business called Life Science Products (LSP) and in 1973 they began production of Kepone in a renovated former Hopewell service station.

Kepone is a member of the chemical group called “chlorinated pesticides”.  This group also includes other more well known insecticides like DDT, chlordane and heptachlor.  Since the 1970s, the use of almost all of these chlorinated pesticides has been banned in the US and abroad.   The chemical structure of Kepone is complex and unlike any naturally occurring substance.  As a result, Kepone is resists natural degradation and is persistent in the environment.  Also like other chlorinated pesticides it bio-concentrates up the food chain.  However, unlike some other chlorinated pesticides, it can be very toxic to people.

LSP’s attention to employee safety and house keeping practices were somewhere between lax and downright sloppy.  There are newspaper accounts of Kepone powder blowing like snow in the wind and forming dunes on and off of the plant’s property.  The adverse health effects caused by Kepone exposures began to surface when LSP’s employees started exhibiting the severe neurological symptoms indicative of Kepone poisoning. Ultimately 30 LSP employees were hospitalized and more than 50 were seriously poisoned.  Testing of other exposed people  in Hopewell (mostly family members of employees) identified that more than 200 had Kepone body burdens higher than was considered safe.  Ultimately the problems drew the attention of the federal government.

Quoting from one incident report:

“CDC (Center for Disease Control) investigators inspected the LSP facility and were appalled to find Kepone everywhere. One CDC epidemiologist reported that, “…there were 3 to 4 inches of the material on the ground…There was a 1 to 2 inch layer of Kepone dust encrusting everything in the plant.” Analyses of the air within the plant indicated that the employees inhaled 30,000 μg of Kepone per day. This stands in contrast to the federal government acceptable limit of 10 μg/day.”

However, even this report did not capture the full extent of the problem as it was estimated that 10-20 tons of Kepone had been discharged directly to the James River.  The river ecosystem was devastated with significant impacts to birds, fish and other wildlife.  The entire previously productive fishery between Hopewell and the Chesapeake Bay (100 river miles) was for years out of health concerns and 4,000 people involved in the James River fishery lost their jobs.   The fishery was not reopened until decades later after clean sediments finally buried the Kepone under a thick layer of silty mud.

The Kepone incident received broad national attention.  Dan Rather and the 60 Minute investigative team did a long segment on Kepone and the Hopewell plant.  There were clips of Dan Rather on the roof of LSP’s building pushing around mounds of Kepone dust.  Kepone was also the lead story in Time magazine.  The governors of Virginia and Maryland demanded that the recently formed USEPA conduct a federal investigation and several Congressional hearings were held.

Kepone’s Political Fallout

The Kepone incident pushed public sentiment well passed the tipping point on the issue of toxic substances regulation; the uproar and resulting political pressure overcame the House of Representative’s resistance to the passage of TSCA.  In 1976, after a five year wait, TSCA was finally passed by large majorities in both the Senate and the House.  President Gerald Ford signed the bill into law.

Epilogue

The original 1970 version of TSCA authored by the Council on Environmental Quality and submitted to Congress in 1971 did not contain the provision directing EPA to regulate PCBs (aka Section 6(e)); it did not mention PCBs at all.  Section 6(e) first appeared as an amendment to the 1975 Senate bill and  there was strong advocacy in favor of it by environmental groups and labor unions.  But, the Senate rejected the amendment because the majority considered the 6 (e) language to be too technically specific for inclusion in the Act and because the USEPA Administrator, Russell Train, argued strongly against its inclusion.

However, despite this earlier rejection, section 6(e) was re-proposed as an amendment to the Senate’s 1976 TSCA bill by Senator Gaylord Nelson of Wisconsin.  Nelson correctly sensed that, as a result of the Kepone incident, the political ground had shifted and the time was now right to get TSCA passed with section 6(e).  With the maelstrom of Kepone publicity swirling around, Nelson’s amendment was accepted into the Senate bill without resistance on the last day of debate. 

Meanwhile, Representative John Dingell of Michigan offered Section 6(e) as an amendment to the House TSCA bill.  Unlike in the Senate, there was spirited opposition to the amendment in the House.  However, even in the House, public outrage over the Kepone incident trumped all other considerations in the representative’s minds.  The amendment was quickly adopted and the bill moved on to President Ford’s desk with Section 6(e) intact.  Thus was born the PCB regulations.


Before beginning this post we at OTO want to express our deepest sympathies to the individuals and families who experienced losses in the wake of the horrible Boston Marathon bombing.  We also want to extend our gratitude to the medical teams that helped the injured and to our local, state and federal law enforcement officers who worked tirelessly to bring order back to the Commonwealth.

PCBs in Soil around Buildings

One of the questions that often come up after soil is tested for PCBs in the vicinity of a building is: why are there higher concentrations of PCBs in the soil right around building foundations?  There has been a tendency for investigators to shrug their shoulders and answer: it must be from the degradation of PCB containing caulk or paint used on the outside of the building.  Frequently there is no direct evidence to support this claim, but it seems like the only reasonable explanation that is consistent with the findings.  Well here is another explanation that might also make sense. 

PCBs in Pesticide Formulations

In the 1950s and ‘60s it was common to treat the soil volume immediately around building foundations with pesticides to control or prevent infestations of soil dwelling insects (like termites, ants etc.).  Solutions of pesticides were pumped into the ground under pressure until the surface soil became wetted.  Among the pesticides commonly used in this way were lindane and several of the other chlorinated pesticides.  Since the chlorinated pesticides were very effective and more persistent in the subsurface environment than other options, they were often the pesticide of choice for this purpose.

Although pesticide registrations are now overseen by the USEPA, before there was an EPA (pre-1970) it was handled by the US Department of Agriculture (USDA).  The USDA has generally had a more “congenial” relationship with farmers and other agricultural enterprises than the EPA has had with farmers and the rest of US industry.  During the period when USDA regulated pesticides it was not out of the ordinary for the USDA to make recommendations on the more effective use of pesticides including pesticides for the control of soil dwelling insects.

One of the ways that pesticides lose their potency (even in the ground) is through the volatilization of the active component into air and via the solublization of the  pesticide into water percolating through the soil.   USDA researchers discovered that the addition of certain oils and/or chemicals to a pesticide formulation prior to its application could inhibit the volatilization and solublization of pesticides thereby increasing the amount of time a single application would remain effective.  Further, it was discovered that one of the very best additives for extending the useful duration of a pesticide applications was polychlorinated biphenyls (PCBs).  PCBs did not modify the pesticide’s mode of toxic action, but they did extend the effective duration of a pesticide application up to ten times over a control application that contained no such additive.

This meant that the addition of a relatively small amount of PCBs to a pesticide formulation could significantly increase the value of a single application.  This obviously presented a significant economic incentive for the inclusion of PCBs into pesticide formulations.  The use of PCBs in this manner was actually encouraged by the USDA because it reduced the total amount of pesticide required to control insects in any given situation.

All that Remains

The last pesticide application that included PCBs likely occurred more than 40 years ago.

While it is possible that some detectable trace of the active pesticide ingredient still remains where it was applied, it is more likely that simple volatilization and the aggressive soil biochemical environment has attenuated the pesticide concentrations so they are too low to measure.  However, it is likely that the PCBs used in that long ago application are still present in the soil and can still be readily measured.

For help understanding how PCBs entered soil at a property please contact me at okun@oto-env.com.


In a regulatory reinterpretation with far significant implications, the USEPA clarified the definition of “Excluded PCB Products” as used in the PCB regulations and signaled its intention to deemphasize the regulation of low concentration PCBs in commercial products.  Excluded PCB products are defined as commercial products containing PCBs originating from Aroclor or non-Aroclor sources where the PCBs are present at less than 50 ppm.

The excluded product reinterpretation was the result of a request by the Institute of Scrap and Recycling Industries, Inc. (ISRI) which was seeking clarification on the management of plastic residue from automobile shredding and recycling.  This plastic residue sometimes contains low levels (less than 50 ppm) PCBs.  Managing the material as a PCB remediation waste limited the recycling industry’s ability to reuse this plastic and increased the cost of the recycling operations.  If it was clearly understood to be an excluded product, then the regulatory burden would be less.

There is often confusion about whether a PCB containing product with less than 50 ppm PCBs should be classified as an Excluded PCB Product or as a PCB Remediation Waste.  The responsibility for making this decision rests with the waste generator, but complicating the assessment is the sometimes variable guidance between EPA regions.   Remediation waste must be managed in accordance with regulatory requirements, excluded product waste is effectively deregulated.  For generators the differences in the management costs and potential long term liabilities between the classifications can be large.

The reinterpretation establishes guidance from EPA headquarters that should assist generators in making the decision.  EPA restated its policy that most materials containing less than 50 ppm PCB are not regulated by the PCB regulations.  The reinterpretation also seems to lessen the burden of proof for generators who claim their material should be classified as an excluded product.  Here is a key quote from the reinterpretation:

“In promulgating the excluded PCB product rule, EPA described the provision as follows:

“EPA is adopting the generic 50 ppm exclusion for the processing, distribution in commerce, and use, based on the Agency’s determination that the use, processing, and distribution in commerce of products with less than 50 ppm PCB concentration will not generally present an unreasonable risk of injury to health or the environment. EPA could not possibly identify and assess the potential exposures from all the products which may be contaminated with PCBs at less than 50 ppm. . . . EPA has concluded that the costs associated with the strict prohibition on PCB activities are large and outweigh the risks posed by these activities. 53 FR 24210 (June 27, 1988).

“EPA has further stated, with respect to the excluded PCB products rule: “These amendments have excluded the majority of low-level PCB activities (less than 50 ppm) from regulation” (Ref. 4). Given the difficulty of determining the precise source of PCBs, EPA believes the purpose of excluding “old” PCBs under the excluded products rule is best effectuated in these circumstances by treating < 50 ppm materials entering a shredder as excluded PCB products unless there is information specifically indicating that the materials do not qualify”.

The reference to the “excluded PCB product rule” refers to a 1988 PCB regulation amendment that confirmed EPA’s intention to not regulate most PCBs at concentrations less than 50 ppm.  The history behind he excluded product rule is a story unto itself (maybe for another post).

Over the past few years the relevance of the 1988 excluded product rule has been cast in some doubt.  However, with this new interpretation EPA has affirmed its decision to not regulate most PCBs at concentrations less than 50 ppm and has clearly reiterated its long standing position “that the use, processing, and distribution in commerce of products with less than 50 ppm PCB concentration will not generally present an unreasonable risk of injury to health or the environment”.

For help with PCB waste classifications please contact Jim Okun at okun@oto-env.com.


From a professional perspective, PCBs entered my life in 1978 while I was post-grad research associate at the U of Hawaii College of Tropical Agriculture.  The mission of our lab was to develop data in support of EPA pesticide registrations for tropical crops.  Pesticide registration is normally conducted by the pesticide manufacturers, but tropical crops are such a small niche market, that it isn’t worth their trouble in most cases.

One day the lab director brought a box with ten 8-ounce jars into my work area and put them down on my lab bench (tangential comment – this is the work area from which I had a view of three waterfalls, sigh).  He told me each of the jars contained a different Aroclor PCB mixture and that the Hawaiian electric company wanted us to develop an analytical method to measure the amount of PCBs in transformer mineral oil.  For the next couple of months, while working up the analytical method, these jars were front and center on my lab bench.  These were not laboratory prepared analytical standards; these were jars containing pure (“neat” to you chemists) Aroclors.

As a young chemist the opportunity to work on an environmentally relevant project was a real thrill.  As you likely know, the percent of chlorine in an Aroclor is indicated by the last 2 digits in the model number; so Aroclor 1221 contains 21% chlorine by mass and Aroclor 1268 contains 68% chlorine (Note: this numbering does not apply to Aroclor 1016 which is a modified version of Aroclor 1242 and thus contains 42% chlorine).  The lighter Aroclors like 1221 and 1232 were as thin as machine oil.  The mid weight Aroclors (1248 and 1254) were as viscous as motor oil.  Aroclor 1268 was pretty much a solid at room temperature.  Also, the lighter Aroclors were clear and the heavier ones had a darker quality to them.

On the chemistry side, there are 209 different PCB molecules (called “congeners”), and each of the Aroclors is a mixture of 50 or more of these congeners.  Chemists sometimes organize the different congeners into groups based on the number of chlorine atoms they have and these groupings are called “homologs”.  So for instance, all the different congeners that have three chlorines belong to the tri-chloro homolog group, all the congeners with four chlorines belong to the tetra-chloro homolog group, and so on.

There is an interesting difference among the Aroclors (interesting to me at least) that even many chemists are not aware of; each Aroclor PCB mixture is dominated by a different homolog group.  So for instance, Aroclor 1221 is made up of 60% mono-chloro congeners (one chlorine), Aroclor 1248 is 56% tetra-chloro congeners (four chlorines), and Aroclor 1262 is 47% hepta-chloro congeners (seven chlorines).  This formulation was not created by design; it was just an accident of the manufacturing process.

Meanwhile back at my lab at the U of H, and many, many gas chromatographic runs later, I did finally come up with a reliable method for measuring PCBs in transformer oil.  Remember this was before there was an SW-846 (EPA’s compendium of analytical methods) or a Method 8082 (EPA’s PCB analytical method).  The method I developed for measuring PCBs in transformer oils was actually published in the Journal of Chromatography (JOC) and the article can still be obtained on-line (the link is for the curious, but purchase is not recommended since this method has been superseded by better USEPA analytical procedures).

When I looked up the link to the JOC article to include with this post I was disappointed to see that the U of H College of Tropical Agriculture now has a trendier name, the “Department of Agricultural Biochemistry”.  On the other hand, I was very pleased that when I clicked my name on the author list my address came up as “University of Hawaii, 1800 East-West Road, Honolulu, Hawaii”;  on a cold windy late winter day it’s nice to still have an address in Hawaii.

In closing, let me acknowledge Dr. James Ogata who directed my work at the U of H lab and who prepared the manuscript for publication.

For help with PCB chemistry questions, please contact me at okun@oto-env.com.


Following months of internal review, the USEPA has decided to broaden its interpretation of the “PCB bulk products” definition under the PCB regulations, 40 CFR 761 (see EPA memorandum).  This change benefits the regulated community by simplifying the removal of PCBs from buildings.

BACKGROUND

On February 29th this year, EPA published a Federal Register notice soliciting comments on a proposal to reinterpret its definition of PCB bulk product waste.  PCB bulk product waste includes building materials like PCB containing caulk, paints and other surface finishes.  The PCB regulations are relatively lenient towards the management of these materials, allowing them to be removed and disposed of in municipal landfills without the notification or specific permission of EPA.  These PCB bulk products often have a PCB content of 10% PCB or even greater.

PCB bulk products frequently contaminate abutting building materials, such as brick, concrete and wood.   However, these abutting materials have not been considered to be bulk products under the regulations, instead they were classified as “remediation waste”.  Although this remediation waste generally contained much lower PCB concentrations than the bulk product contamination source, it was subject to stricter management requirements.  These management requirements included notifying of EPA of its presence, obtaining approval of a remediation plan and disposal of the material at a TSCA permitted landfill.  The new interpretation partially levels the playing field.

WHAT THE CHANGE DOES AND DOES NOT INCLUDE

Going forward, the materials that became PCB contaminated due to their proximity to bulk products may also be managed as PCB bulk products instead of being managed as remediation waste; this is a significant improvement over the previous interpretation.  However, there is an important consideration to keep in mind when planning a PCB bulk product removal project.  The reinterpretation only applies when the original bulk product is still adhering to the contaminated abutting material at the time the material is designated for disposal.  If this designation does not take place before the bulk product is removed, then like Cinderella’s carriage turning back into a pumpkin, the abutting PCBs turn back into a remediation waste.

For help on differentiating between PCB remediation waste and PCB bulk products, please reach me at okun@oto-env.com.


With PCBs (polychlorinated biphenyls) being more in the news, you may hear the terms “Aroclors”, “homologs” and “congeners” used to describe the different ways that PCBs are measured.  Measuring the concentration of PCBs gets complicated because there are actually 209 different chemicals (referred to as congeners) included in the PCB chemical group.  Measuring all 209 congeners separately is research level analytical chemistry and is impractical for most purposes.  However, analytical chemists have developed a number of effective ways to measure PCBs that don’t require looking for all 209 different PCB congeners.

Measuring PCBs as Aroclors

The most common way to measure PCBs is as Aroclors.  Aroclor was the trade name of the commercial PCB mixtures manufactured by the Monsanto Chemical Company and sold in the United States.  An Aroclor PCB mixture might consist of over 100 different individual PCB congeners, although 10-20 might make up over 50% of the mixture.   When analytical chemists test a sample to see if it has an Aroclor PCB mixture in it, they look for a distinctive gas chromatographic pattern (sometimes called a chromatographic “fingerprint”) that is indicative of one of the Aroclors.  There were  nine common PCB Aroclor mixtures (1221, 1232, 1242, 1016, 1248, 1254, 1260, 1262, and 1268), and each of them has a distinctive gas chromatographic pattern.  Measuring PCBs as Aroclors relies on there being a relatively fixed composition of PCB congeners in the mixture.

When a chemist measures the amount of Aroclor in a sample, they will know the total amount of that Aroclor that is present, but will not know the identity or the concentration of the specific PCB congeners in the sample.  Provided the sample has not been subjected to conditions that might degrade or change the composition of the PCBs, knowing the type of Aroclor present and its concentration is usually sufficient for environmental assessment.

Homologs – For When Sample Weathering Has Occured

However, if an environmental sample has been subjected to conditions that might alter the congener composition of the sample, then it will be more accurate to test the sample by a different method.  Air samples, sediment samples, biota samples and water samples are the ones most likely to have had their congener composition changed by environmental conditions.  This can happen because the PCB congeners with fewer chlorine atoms tend to partition into air and water more readily than those with more chlorine atoms.  For this reason air and water samples are likely to be “enriched” with congeners with fewer chlorine atoms.  Biota samples can also be subject to bio-degradation with some congeners being selectively reduced and others remaining constant.

For samples whose congener makeup has been altered, testing for Aroclors will give erroneous results.  Testing for PCB homologs will give more reliable results for these samples.  Homologs are a way of grouping PCB congeners by the number of chlorine atoms they have; this can vary from one to ten.  All the PCB chemicals that have the same number of chlorine atoms are said to belong to the same homolog group.  There are 11 different di-chloro congeners in the 2-chlorine homolog group and there are 42 different tetra-chloro congeners  in the 4-chlorine homolog group, as examples.  Laboratory results for PCB homologs will list the the amount of PCB present in the sample by the number of chlorine atoms.

But, Sometimes Only Congener Analysis Will Do

In circumstances requiring more congener detail than can be provided by either Aroclor or homolog analyses, it is also possible to analyze samples for a subset of the full 209 congeners.  Analyzing samples for the full 209 congeners is, as I said before, still research level chemistry.  The NOAA PCB congener method cites 20 congeners to be reported, this is often used for sediment analysis. The USACE PCB congener method cites 22 congeners to be reported. The SW-846 8082 method cites 19 congeners to be reported. The WHO lists cites 12 congeners (those which the World Health Organization believes pose the greatest health concern – although this is disputed).  Congener data is particularly useful for forensic purposes, but the guidance available for interpreting the data is fairly limited.

Overall, in most instances measuring PCBs using the Aroclor method will be the best choice.  Where that method is inappropriate, looking at homologs is likely to be a good option, and where even more detailed results are needed, looking for PCB congeners will be necessary.  For homolog and congener testing make sure to select a laboratory with considerable experience with those analyses as they are challenging tests to perform.

For help selecting analytical methods or designing a PCB assessment program, please contact me at okun@oto-env.com.


In schools and other buildings where there is concern about exposures to PCBs, inhalation of contaminated air is usually the exposure pathway of greatest concern.  However, few, if any, laboratory studies have specifically considered whether the inhalation of PCBs results in the same or different health effects than those observed when PCBs are ingested.

In their risk assessment models, the USEPA assumes that exposure to PCBs by all routes of exposure are toxicologically equivalent.  Since most or all of the animal toxicity studies used to assess PCBs have been feeding studies (using the ingestion pathway), this is the mode of exposure that we know the most about.  However, there are some good reasons to suspect that inhalation exposures may be different from ingestion due to the way PCBs behave once they enter the body.  This is particularly true because the liver is one of the principle target organs for PCBs.

When any toxic material is ingested (or a pharmaceutical product for that matter) absorption usually begins in the stomach and is generally completed in the small intestine.  As chemicals are transferred into the circulatory system from the digestive organs, their first destination in the body is the liver.  So if a chemical gives rise to liver toxicity, ingestion can be a particularly damaging route of administration because the toxic material proceeds directly to the liver from the digestive tract.

By contrast, when a toxic material is inhaled, it enters the lungs, transfers to the blood, goes to the heart and from there enters the general circulatory system.  By the time an inhaled toxic material reaches the liver, its concentration has been reduced by dilution into the overall volume of blood in the body.  What’s more, in the case of lipid (fat) soluble chemicals like PCBs, a high percentage of the dose entering the body by inhalation will become sequestered in other fatty tissues before the PCBs ever reach the liver.  The overall effect would be to reduce the potential toxicity to the liver.

Interestingly there are pharmaceuticals that exhibit similar effects, testosterone is a good example.  When used as a pharmaceutical, testosterone can not be given orally, that is by ingestion, because it can cause liver toxicity. This is despite the fact that it is a naturally occurring hormone.  However, when given by routes of administration that reduce the concentration that the liver sees at any one time, testosterone does not harm the liver.

At this time I am not aware of good animal studies that test whether inhaled PCBs are in fact less toxic than ingested PCBs.  However, there are a large number of well documented human studies where people were exposed to PCBs by inhalation in occupational settings.  These studies consistently show less toxicity than has been predicted by EPA’s health effects models.  It could be that this lower than expected toxicity is due to inhalation being the exposure pathway for these people rather than ingestion.  If this is true, then it supports the idea that low concentrations of PCBs in air may be less hazardous than thought.