Tag: PCBs

PCB Regulations: The Origin Story

June 3, 2013 Jim Okun

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.

PCBs in Soil around Buildings from Pesticide Applications

April 22, 2013 Jim Okun

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.

EPA Issues Major Reinterpretation on Excluded PCB Products

April 9, 2013 Jim Okun

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.

Differences between the PCB Aroclors

March 13, 2013 Jim Okun

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.

PCBs: Aroclors, Homologs and Congeners

December 19, 2011 Jim Okun

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.

Differences Between Type 1 and Type 2 Aroclor 1254 (PCBs)

September 6, 2011 Jim Okun

Aroclor 1254 was the PCB mixture most commonly used in building materials, based on my personal experience reviewing test results.  Recently, as I was digesting data and researching literature to prepare for my UMass Soils Conference presentation this fall, I discovered something interesting about Aroclor 1254 that I hadn’t known; there are two types of Aroclor 1254, and while they are similar in their physical properties, from the standpoint of environmental toxicology they are very different.

Type 1 Aroclor 1254 was one of the commercial PCB mixtures manufactured and sold by the Monsanto Company prior to 1971; a high percentage of its production was used in electrical equipment like transformers and capacitors, smaller amounts were used in other applications like being formulated into building materials (e.g. paint and caulk).  In its pure form Aroclor 1254 (Type 1 and Type 2) is an highly viscous liquid that is thicker than honey.  While each batch of PCBs differed slightly in its exact chemical composition (based on the percentages of the the individual PCB congeners present), these differences from batch to batch were small. However, around 1971 the formula for making Aroclor 1254 changed in a fundamental way giving rise to what is now referred to as Type 2 Aroclor 1254.

Type 2 Aroclor 1254 was an indirect result of the 1968 Yusho rice oil poisonings. After the Yusho incident, Monsanto (the sole US PCB manufacturer) was seeking alternatives to reduce the toxicity of its PCB mixtures.  They hit on two ideas:

  1. Introducing a new PCB mixture, called Aroclor 1016, that contained lower concentrations of the volatile low molecular weight congeners and the more toxic high molecular weight congeners; and
  2. Stopping the sale of PCBs for use in applications that were not considered to be “totally enclosed”.  The totally enclosed requirement was intended to limit PCB uses that were more likely to result in human or environmental exposures.

Aroclor 1016 was produced by first making Aroclor 1242 (which it resembles), and then through distillation removing the light and heavy ends of the mixture.  As predicted, the toxicity of Aroclor 1016 was significantly less than that of other PCB mixtures; so far so good.   However, at this point in the story you might want to ask: “what happened to the light and heavy ends removed from the Aroclor 1242 to make Aroclor 1016?  Were these simply discarded?”

The answer is no, they were not discarded.  These light and heavy ends were used as feedstock for the manufacture of Type 2 Aroclor 1254.  Type 1 Aroclor 1254 was manufactured as a one step process; biphenyl (derived from coal tar) was chlorinated until the chlorine content in the resulting PCB mixture reached 54%.  In contrast Type 2 Aroclor 1254 was manufactured using a two step process where the by-products of Aroclor 1016 manufacturing (the light and heavy ends) were re-chlorinated to end up with a final product with 54% chlorine.

The physical properties of Type 1 and Type 2 Aroclor 1254 are virtually indistinguishable, but their chemical, toxicological and likely environmental properties have been shown to be different.  Type 2 contains higher concentrations of the so-called “co-planer” congeners (for chemists: that means the ones with no ortho substitutions) including about 5 times more of the three most toxic of these co-planer congeners, PCB 126, PCB 169 and PCB 77.  Type 2 Aroclor 1254 has also been reported to contain significant concentrations of the highly toxic polychlorinated dibenzofurans (PCDFs); these are virtually absent in Type 1 Aroclor 1254.

One interesting question is how much of the total Arochlor 1254 production was Type 2?  The answer from Monsanto’s production records indicates that about 1% of total Aroclor 1254 was Type 2.  Since Monsanto stopped PCB sales for other than totally enclosed uses at about the same time that production of Type 2 Aroclor 1254 began, it is likely that most or all of it went into electrical equipment like transformers and capacitors with little if any going into building materials.

Another interesting observation is that it is likely that Type 2 Aroclor 1254 is the PCB mixture that has been most commonly used in conducting toxicological studies on PCBs.  This is because towards the end of Monsanto’s PCB production (after 1970), most or all of the Aroclor 1254 being produced was Type 2.  As a result, this was the Aroclor 1254 that was available for distribution to researchers when toxicological studies were being undertaken on PCBs.  It took almost 20 years after the end of US PCB production before scientists could detect the chemical differences between Type 1 and Type 2 Aroclor 1254.

For more information please email me at okun@oto-env.com.