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In the United States, hazardous wastes are subject to regulations mandated by the Resource Conservation and Recovery Act (RCRA). Every month, we provide clear, in-depth guidance on a different aspect of the RCRA regulations. The information presented here is an excerpt from McCoy’s RCRA Unraveled, 2020 Edition.

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P- and U-Listed Hazardous Wastes

Regulatory background

The P- and U-wastes are regulated under §261.33—Discarded commercial chemical products, off-specification species, container residues, and spill residues thereof. These commercial chemical products were first regulated on May 19, 1980. Here is how EPA described them:

“EPA intended to encompass those chemical products which possessed toxic or other hazardous properties and which, for various reasons, are sometimes thrown away in pure or undiluted form. The reasons for discarding these materials might be that the materials did not meet required specifications, that inventories were being reduced, or that the product line had changed. The regulation was intended to designate chemicals themselves as hazardous wastes, if discarded, not to list all wastes which might contain these chemical constituents. In drawing up these lists, the agency drew heavily upon previous work by EPA and other organizations identifying substances of particular concern [e.g., the Department of Transportation].” [45 FR 33115]

The so-called P-chemicals, which are identified in §261.33(e), possess “extremely hazardous properties” that make them lethal in very small quantities. [45 FR 33116] These chemicals meet the listing criteria of §261.11(a)(2) and are identified as acute hazardous wastes. If a facility generates a single P-waste (or multiple P-wastes) at a rate of >1 kg/mo, the facility is regulated as an LQG.

The chemicals on the U-list [§261.33(f)] meet the listing criteria of §261.11(a)(3), which identifies various factors that indicate a waste is “toxic.” If a facility only generates one hazardous waste, and if this waste has a U-code, the facility would be regulated as an SQG if the generation rate is between 100 and 1,000 kg/mo. It would be an LQG if the plant generates 1,000 kg/mo or more of the waste.

Practical hints on using the P- and U-list

First, the chemicals on each list are listed twice: the first time in alphabetical order, the second time in numerical order by waste code. If, for some reason you have a waste code (e.g., P024), and you want to find out what chemical corresponds to this hazardous waste number, use the second list, which is formatted in numerical order by waste code. (It turns out that P024 is p-chloroaniline.)

Next, there are some inconsistencies in chemical nomenclature in the P- and U-lists. The risk here is that, if you can’t find the chemical you are getting ready to discard on either list, you could conclude that your chemical is not regulated, when in fact you’re looking in the wrong place or perhaps are using a different chemical name than EPA used. To avoid these problems, we like to use the “List of Lists.” This publication not only consistently alphabetizes chemicals, but it also identifies chemicals by common synonyms. For example, 1,1,1-trichloroethane is also known as methyl chloroform, which is hazardous waste number U226. The “List of Lists” is accessible online at

CAS numbers, variants, and isomers

Although the P- and U-lists also cross reference chemical names to Chemical Abstracts Service (CAS) numbers, this information needs to be used with care. For example, you may be using a chemical name that is different from the one EPA uses. If you can look up the CAS number for your chemical in the CAS Collective Index or some other reference and compare it with the CAS number in the P- or U-list, the listed waste code will apply if the numbers are identical.

However, it is not safe to assume that only the CAS number given in the P- or U-listing is regulated. For example, anhydrous cyclophosphamide (CAS No. 50-18-0) is listed as U058. Because this compound is hygroscopic, it readily hydrates to cyclophosphamide monohydrate (CAS No. 6055-19-2). EPA says that because both compounds are known generically as “cyclophosphamide,” they are both U058 when disposed. [RO 11687] Anhydrous chloral (U034) and chloral hydrate are also regulated in the same manner; that is, they are both U034 even though their CAS numbers are different. [RO 14175]

A related situation occurs with chemical isomers. For example, toluenediamine has many isomers, including toluene-2,4-diamine (CAS No. 95-80-7) and toluene-2,6-diamine (CAS No. 823-40-5). The U-list contains U221—toluenediamine (CAS No. 25376-45-8). At first glance, it might appear that neither toluene-2,4-diamine nor toluene-2,6-diamine are listed hazardous wastes because their CAS numbers don’t correspond with the U-listing. However, the CAS number in the listing is for generic toluenediamine mixed isomers, which means that both isomers identified above are U221 when disposed. [RO 13760]

If EPA designates a specific isomer, then only that isomer is covered by the listing. For example, U140—isobutyl alcohol (CAS No. 78-83-1) covers only this isomer; n-butyl alcohol is not U140 (it’s U031). [RO 13760]

Some of the P- and U-listings specify a parent compound and “salts” or “esters” of that compound (e.g., P075—nicotine & salts). If a parent compound is listed, but the salt or ester of that compound is not, then only the parent compound is regulated. [RO 12155] For example, dinoseb is listed as P020; no salts are listed. Therefore, if a product consists of “sodium dinoseb,” it is not P020. [RO 11489] Similarly, EPA has clarified that epinephrine salts are not included in the scope of the P042 hazardous waste listing. P042 applies only when epinephrine base (CAS No. 51-43-4) is discarded unused. [RO 14778] The agency has gone on to say the same reasoning applies to the disposal of unused phentermine. Only phentermine base (CAS No. 122-09-8) has the potential to meet the P046 listing description. [RO 14831] This guidance is significant because many of the pharmaceuticals in use in hospitals and other medical applications are in the form of salts or esters.

Hazard codes

Some of the chemicals on the P- and U-list are followed by one or more letters in parentheses; these are hazard codes. Per §261.33(e), all P-listed chemicals are acute hazardous wastes and have a hazard code of (H) [hazard codes are explained in §261.30(b)]. If a letter does not follow a chemical on the P-list, the chemical is an acute hazardous waste due to its acute toxicity. If a chemical on the P-list is followed by one or more hazard codes in parentheses, the chemical is acutely hazardous for that property or properties. For example, the first P-waste in the §261.33(e) alphabetical list, P023—acetaldehyde, chloro-, is not followed by any hazard code in parentheses and would, therefore, be an acute hazardous waste due to acute toxicity [with complete hazard code (H, T)]. On the other hand, P006—aluminum phosphide, is followed by “(R, T),” which means that this chemical is acutely hazardous due both to its reactivity and acute toxicity [and would have a complete hazard code of (H, R, T)].

Three of the P-wastes (P009, P081, and P112) have a hazard code of (R) following the chemical name. This means that they are acutely hazardous only due to their reactivity (e.g., P081 is nitroglycerine). “EPA has also defined this [P-listed] category of wastes to include wastes, such as explosives, which otherwise meet…the statutory definition of hazardous waste. This has been done in recognition that wastes may be acutely hazardous even if they are not toxic.” [May 19, 1980; 45 FR 33106]

If a letter does not follow a chemical on the U-list, the chemical was placed on this list due to its toxicity and is assumed to have a (T) hazard code. Conversely, if a letter in parentheses follows the chemical name, the chemical was added only for that reason [e.g., U001—acetaldehyde has an “(I)” following it, indicating that it was listed solely due to its ignitability—not toxicity and ignitability].

These hazard codes have three practical functions. First, all acute hazardous wastes [i.e., those with an (H) code, including all P-wastes] have a regulatory threshold of 1 kg/mo when determining generator status per Table 1 of §262.13. Second, containers of acute hazardous wastes (including all P-wastes) must be triple rinsed before they are empty per §261.7(b)(3). Third, P- and U-wastes followed only by an (I), (C), or (R) are eligible for the special provisions of §261.3(g).

Tip for identifying commercial chemical products

The most common mistake we encounter with P- and U-wastes is that people tend to overuse these codes; they erroneously conclude that they have a P- or U-waste. For example, a generator analyzes its waste and finds that it contains one or more of the chemicals on the P- or U-list. The generator then applies the waste codes associated with any such chemicals that it identifies and must then manage the waste according to all applicable RCRA rules. Alternatively, the generator starts looking for the chemicals in Appendix VIII of Part 261. Unfortunately, this appendix gives waste codes that might be associated with various chemicals.

Here is a conceptual tool that we sometimes find useful in deciding whether a material is a listed P- or U-waste. Visualize the label on a container of the material in question. If the label uses one of the generic chemical names from the P- or U-list to describe the contents of the container, the material is a listed P- or U-waste when disposed. If the label uses a name or term that is not on the P- or U-list, the material is probably not P- or U-listed (unless it contains a P- or U-listed chemical as the sole active ingredient, as will be discussed later).

For example, consider an unused mercury thermometer that we intend to discard. Thermometers would typically be stored/shipped in a box, and the label on the box would say “Thermometer.” When you look on the P- or U-list, the word “Thermometer” doesn’t appear; hence, the thermometer is not a listed waste. (The thermometer is actually a manufactured article that contains mercury and would only be hazardous if it exhibits a characteristic—probably D009.) [RO 13310, 14012] Compare this against a vial of unused mercury that we intend to discard. The label on the vial would say “Mercury,” which is listed as U151. The vial of mercury would be U151 hazardous waste.

Creosote-containing railroad ties are to be disposed. Creosote appears on the U-list as U051; are the ties listed hazardous waste U051?

The label on a bundle of ties would read “Railroad ties.” The label does not say “Creosote.” Therefore, unless the ties exhibit a characteristic, they are not hazardous waste. [RO 11094, 11104, 11129, 11535, 12012] However, note the following twist. A facility bakes used railroad ties to recover creosote, and then uses the recovered creosote as a wood preservative without further processing. The reclaimed creosote is again a commercial chemical product (i.e., the label on a drum of this material would say “Creosote”). If spilled or discarded, this recovered material would be hazardous waste U051. [RO 13572]

Unused paint that contains xylene is being discarded. Xylene appears on the U-list as U239; is the discarded paint U239?

No. The label on the container says “Paint” not “Xylene.” If the paint exhibits the characteristic of ignitability, it would be D001. [RO 11180]

What is a “commercial chemical product”?

If you read the text of the regulations in §261.33(a) through (d), you will find references to a number of materials that are regulated as commercial chemical products (CCPs). These materials include:

  1. Pure, unused chemicals having the generic name given in the P- or U-list;
  2. Manufacturing chemical intermediates having these names;
  3. Off-specification variants of 1 or 2 above;
  4. Residues of these chemicals in containers that do not meet the definition of “RCRA-empty”; and
  5. Residue and debris resulting from the cleanup of spills of these chemicals.
The only definition of these terms appears in the comment included in §261.33(d) that is part of the regulations:

Comment: The phrase ‘commercial chemical product or manufacturing chemical intermediate having the generic name listed in…’ refers to a chemical substance which is manufactured or formulated for commercial or manufacturing use which consists of the commercially pure grade of the chemical, any technical grades of the chemical that are produced or marketed, and all formulations in which the chemical is the sole active ingredient. It does not refer to a material, such as a manufacturing process waste, that contains any of the substances listed in [the P- or U-list]. Where a manufacturing process waste is deemed to be a hazardous waste because it contains a substance listed in [the P- or U-list], such waste will be listed [either as an F- or K-waste] or will be identified as a hazardous waste by the characteristics….”

Although this comment is helpful, it introduces several more terms that need interpretation:
  1. Technical grades of the chemical;
  2. Sole active ingredient; and
  3. Manufacturing process wastes.

Pure, unused chemicals

Pure, unused chemicals are CCPs. The general concept behind the regulation of pure, unused chemicals is that these are very concentrated (and, hence, very hazardous) materials. If improperly disposed, they would pose a significant threat to human health or the environment. Common situations that involve such chemicals include disposal of 1) excess or unsaleable inventory; 2) laboratory chemicals that are no longer needed, that are past an expiration date, or that are suspected of being contaminated or otherwise impure; and 3) feedstock or product from a process that is being shut down.

Unfortunately, EPA doesn’t define the term “pure.” As a result, a common concern in the regulated community is whether a waste that contains one or more of the P- or U-listed substances as a constituent must be managed as hazardous. EPA addressed this by noting:

“The intent of the regulation was to encompass only those materials which were being thrown away in their pure form or as an off-specification species of the listed material…. [T]he regulatory language has been clarified to restrict the application of [the P- and U-listings] to chemical products, or their off-specification species, and not to wastes which contain these materials as constituents.” [May 19, 1980; 45 FR 33115–6]

Where a chemical contains more than one constituent (i.e., it is impure), the agency captures such chemicals as CCPs through the use of other terms, such as “sole active ingredient” or “technical grade of a chemical,” as will be discussed later. In most cases, if the main entry on the label on whatever you are discarding is the name of a chemical on the P- or U-list, it will be pure enough to be regulated.

To be regulated as this class of materials, the chemical cannot have been used. [RO 11202, 14686] “Only unused chemicals are considered commercial chemical products that could carry a ‘P-listed’ [or U-listed] waste code. Once a…chemical that is on the P-list [or U-list] has been used, it is not considered a commercial chemical product.” [May 23, 2006; 71 FR 29725]

Chemicals used for their intended purpose

When a CCP is used for its intended purpose, it will not meet the listing description for any of the P- or U-wastes, since it has been used. [July 28, 1989; 54 FR 31336] Residual contamination that results from this use is only regulated if it meets the listing description for an F- or K-waste (an unlikely situation) or if it exhibits a characteristic.

When a pesticide applicator sprays a U-listed pesticide from his/her crop duster, some of the chemical ends up on the side of the plane that is washed off upon landing. Is the washwater a U-listed hazardous waste when disposed?

No. “The agency does not believe that the pesticide residue left on the aircraft is a discarded commercial chemical product. The residue does not qualify as material discarded or intended to be discarded…. In listing commercial chemical products, EPA intended to cover those products which, for various reasons, are thrown away. The agency did not intend to cover these cases, as here, when the chemical is released into the environment as a result of use. Unless we take such a position, one could argue that the pesticide that is sprayed that does not fall directly on the crop (but falls on the ground next to the crop) would be disposal of an unused commercial chemical product; such an interpretation is a distortion of the commercial chemical product rule…. Rather, this rinsewater would be defined as hazardous only if it exhibits one or more of the characteristics.” [RO 11096] See also RO 11160 that applies the same reasoning to washing the exterior of trucks and service vehicles.

When this interpretation was challenged by an EPA regional office, headquarters reaffirmed it and added the following twist: “Since the pesticide has been sprayed from the airplane, it technically has been used and, therefore, is not defined as a §261.33 commercial chemical product. (On the other hand, the pesticide residue that remains in the spray tanks after the spraying operation has not technically been used and, thus, would be defined as a commercial chemical product.)” [RO 11115]

In other examples where chlordane was used as a pesticide and resulted in soil contamination, EPA cited §261.2(c)(1)(ii), which states that P- or U-commercial chemical products are not solid wastes if they are applied to the land and that is their ordinary manner of use. The soil would be a hazardous waste only if it is excavated and exhibits a characteristic. [RO 11182, 12357] Similarly, spent ash from fumigation with aluminum phosphide (P006) is not a listed CCP because the chemical has been used (although the ash could exhibit a characteristic and be a regulated hazardous waste). [RO 11202]

Manufactured articles aren’t P- or U-wastes

One of the most common errors in applying the P- and U-codes is that generators analyze an object, find that it contains one or more of the listed chemicals, and then assign the associated hazardous waste code(s) to the object when they are getting ready to discard it. In general, EPA would term these objects “manufactured articles” and regulates them as follows:

“Manufactured articles that contain any of the chemicals listed [on the P- or U-list] are rarely, if ever, known by the generic name of the chemical(s) they contain and, therefore, are not covered by the [P- or U-] listings.” [November 25, 1980; 45 FR 78541]

For example, wool blankets that were treated with DDT will be discarded. The blankets are manufactured articles containing DDT (which keeps moths from eating the blankets), and they would not be U061—DDT when disposed. [RO 11711] We mentioned that thermometers, even if unused, are actually manufactured articles that contain mercury and would only be hazardous if they exhibit a characteristic. [RO 13310, 14012]

EPA provided additional guidance to differentiate between commercial chemical products and manufactured articles in RO 14887. The agency noted manufactured articles, such as batteries, fluorescent lamps, and thermometers, are all designed for a purpose other than to access the chemicals that are present in these articles. Specifically, one uses these articles for electrical energy (batteries), for light (lamps), or to measure temperature (thermometers). One does not use these articles in order to access the mercury or lead or other chemicals contained in them.

What about a medical device that delivers nitric oxide (NO) therapy to patients? When the device is activated, an ampule containing liquid dinitrogen tetroxide (N2O4) is broken, releasing nitrogen dioxide (NO2) gas. The NO2 is then converted to NO while it passes through tubing that contains a catalyst. The agency noted the following:

  • Pure, unused NO2 is P078 when discarded. In addition, the liquid N2O4 dimer is also included within the P078 listing because N2O4 forms when NO2 gas is compressed. The device contains commercially pure or technical-grade compressed NO2 gas within the glass ampule, which is also the sole active ingredient. Therefore, if the glass ampule is not broken, then the unused device containing the compressed NO2 is a commercial chemical product and is regulated as P078 when discarded. This situation may occur if inventory expires or exceeds its shelf-life and is disposed.
  • The unused device would not be a manufactured article, because a patient/individual specifically intends to access the chemical inside the device.
  • If the device is used as intended, the used device is not regulated as a listed hazardous waste when discarded. This is because once the glass ampule has been broken, the device reaches atmospheric pressure and meets the definition of RCRA-empty, as defined in §261.7(b)(2). [RO 14887]

Manufacturing chemical intermediates

When EPA regulated the CCPs, their intent was to capture those materials that are typically highly concentrated and that are sometimes disposed or spilled. The agency realized, however, that these chemicals might not always be sold as products. For example, in a chemical plant, a chemical might be produced in one process and then fed directly to another process as feedstock. In this case, the chemical is a “manufacturing chemical intermediate” rather than a “product.” Nevertheless, the intermediate would pose the same threat to human health and the environment if discarded or spilled. Therefore, EPA decided to include these manufacturing chemical intermediates under the listing criteria for P- and U-wastes.

The agency has not provided any general guidance or definitions on how to identify a manufacturing chemical intermediate in the real world. Our advice is to rely on the knowledge of process engineers or operators who are familiar with the operation of a plant. Ask these people “What’s in that pipe, tank, container, etc.?” If the answer is “Benzene” (or some other chemical on the P- or U-list), you are probably dealing with a manufacturing chemical intermediate or a CCP.

If their answer is more process related, like “Bottoms from the stripper tower,” you will have to inquire about its composition. If the answer is something like “It’s a mixture of benzene, toluene, and other stuff,” you are not dealing with a regulated manufacturing chemical intermediate because it is not predominantly a single chemical. As always, if you’re not sure whether the material is regulated, ask your regulator for a case-specific determination.

Off-specification commercial chemical products

The general concept of off-specification CCPs is that sometimes products contain contaminants that would prevent them from being sold or used as products. In guidance, EPA described an off-spec CCP as “an unused material that would have been a CCP if it met specifications.” [RO 14194]

Typically, this would occur at a manufacturing plant where something went awry in the production process, and the material is rejected after quality assurance (QA) testing as not meeting product specifications. Sometimes, a product might be rejected by a customer’s QA procedures, and the product would be returned to the manufacturer. Because off-spec variants are probably as hazardous as on-spec products, EPA wanted to regulate them as P- or U-listed wastes when disposed or spilled.

A manufacturer stores product formaldehyde (CAS No. 50-00-0) in containers before use in a manufacturing process. While in storage, some of the formaldehyde polymerizes to form paraformaldehyde (CAS No. 30525-89-4), which is unusable in the manufacturing process. The manufacturer separates the paraformaldehyde from the usable formaldehyde and sends the paraformaldehyde for disposal. Unused formaldehyde is U122 when discarded, but unused paraformaldehyde is not on the P- or U-list. When discarded, is the unused paraformaldehyde a listed hazardous waste?

Yes. Paraformaldehyde is an off-specification form of formaldehyde and meets the U122 listing description. When a commercial chemical product listed in §261.33(e) or (f) undergoes a chemical change that renders the chemical off-specification, the applicable P- or U-listing for the original chemical applies, even in cases where the chemical composition has changed sufficiently to require assignment of a different CAS number. [RO 13658]

Container residues

The regulatory language dealing with container residues [§261.33(c)] is pretty much self-explanatory. If a container held a P- or U-chemical, the residue within the container or liner removed from the container retains the P- or U-listing unless the container or liner is “RCRA-empty” per §261.7. Sometimes people overlook the Comment in §261.33(c), which is part of the promulgated regulations and reads as follows:

Comment: Unless the residue is being beneficially used or reused, or legitimately recycled or reclaimed; or being accumulated, stored, transported, or treated prior to such use, reuse, recycling, or reclamation, EPA considers the residue to be intended for discard, and thus, a hazardous waste. An example of a legitimate reuse of the residue would be where the residue remains in the container and the container is used to hold the same commercial chemical product or manufacturing chemical intermediate it previously held. An example of the discard of the residue would be where the drum is sent to a drum reconditioner who reconditions the drum but discards the residue.”

Three unique situations regarding residues in containers are discussed below.

Partially full containers holding unused chemicals

A bottle of P- or U-listed laboratory chemical is opened and some of the chemical is used. What is the regulatory status of the remaining chemical in the bottle when discarded? What about the bottle itself?

According to §261.33(c), the remaining chemical or residue in the bottle is regulated as P- or U-listed hazardous waste unless the container is rendered “RCRA empty” under §261.7(b). What’s more, the bottle would be a hazardous waste container until it is rendered RCRA empty.

This regulatory language is bolstered by EPA guidance in RO 14656. In this guidance, the agency addressed unused solvent residues in spray cans that are being discarded. According to the agency, if the remaining unused solvent in the spray can is P- or U-listed, it would be a listed hazardous waste when discarded.

Used vials and syringes

Several U-listed chemicals are used as drugs in chemotherapy. These include chlorambucil (U035), cyclophosphamide (U058), daunomycin (U059), melphalan (U150), mitomycin C (U010), streptozotocin (U206), and uracil mustard (U237). The drugs are received in vials and dispensed with syringes; how would the used vials and syringes be regulated under RCRA?

If the vials and syringes of drugs are “empty” per §266.507, they are not regulated under RCRA. Otherwise, they are. However, EPA became concerned about the safety issues associated with handling these drugs and provided the following guidance: “The agency is aware, however, that prudent practice dictates that materials contaminated with these chemicals (such as syringes, vials, gloves, gowns, aprons, etc.) not be handled after use. Therefore, to minimize exposure to these toxic chemicals, the agency recommends that the entire volume of waste be weighed and that there be no attempt to remove any residue from the vial before disposal.” [RO 12946] The very small quantity generator exclusion (no more than 100 kg/mo) could apply in these circumstances. [RO 12549, 12946]

In the February 22, 2019 pharmaceuticals rule, EPA promulgated §266.507 in Part 266, Subpart P to provide a new definition of “RCRA-empty” for containers holding hazardous waste pharmaceuticals. [In that rule, EPA also added new §261.7(c), which points users to §266.507 for determining whether containers of hazardous waste pharmaceuticals are RCRA-empty.] This new definition makes it easier to dispose (as nonhazardous) containers that still hold residues of hazardous waste pharmaceuticals but that don’t necessarily meet the existing definition of RCRA-empty in §261.7(b). In §266.507(b), a syringe is considered RCRA-empty provided the contents have been removed by fully depressing the plunger of the syringe. The pharmaceuticals can be removed from the syringe in three ways: 1) fully depressing the plunger of the syringe by administering the contents of the syringe to a patient, 2) fully depressing the plunger of the syringe by injecting the contents of the syringe into another delivery device (e.g., an IV bag), or 3) fully depressing the plunger of the syringe by emptying the remaining contents into a hazardous waste collection container. [84 FR 5906]

If a syringe is not RCRA-empty as described above, the syringe must be placed with its remaining hazardous waste pharmaceuticals into a container that is 1) managed and disposed as a non-creditable hazardous waste pharmaceutical under Subpart P, and 2) managed under any applicable federal, state, and local requirements for sharps containers and medical waste. These empty-container provisions for syringes in §266.507(b) supersede previous agency guidance in RO 13718 and 14788. [84 FR 5906]

EPA addressed cartridges (i.e., small containers) of the nicotine liquid removed from e-cigarettes. When discarded, the cartridges (and the e-cigarette holding them if discarded) are considered P075 wastes. Even if unused cartridges are sent for extraction and reclamation of the nicotine liquid, the cartridges would be P075 if discarded, unless they are rendered RCRA-empty. [RO 14850, 14851] Subsequent to issuing the two RO documents referenced just above, the agency’s February 22, 2019 pharmaceuticals rule noted that “the agency is allowing e-cigarettes, be managed as hazardous waste pharmaceuticals under 40 CFR Part 266, Subpart P when they are discarded.” [84 FR 5826] It is not clear, however, whether the RCRA-empty provisions in §266.507(a) or (d) of Subpart P would apply to vials/cartridges of nicotine-containing e-liquid. The answer may depend on the type of container intended for discard. Until guidance from EPA is available, a conservative approach is to manage e-liquid vials/cartridges as either non-creditable hazardous waste pharmaceuticals under Subpart P or as P075 hazardous waste when discarded. Thus, these vials/cartridges of e-liquid will require hazardous waste management and cannot be simply thrown in the trash (unless the household hazardous waste exclusion applies).

Regulatory status of warfarin residues in containers

Warfarin appears on both the P- and U-lists: warfarin (and its salts) at a concentration of >0.3% is listed as P001 in §261.33(e), while warfarin (and its salts) at a concentration of <0.3% is listed as U248 in §261.33(f). Some warfarin-based pharmaceuticals (brand names Coumadin and Jantoven) will meet the P001 listing description while others will meet the U248 listing if disposed.

As noted in the previous subsection, EPA’s February 22, 2019 pharmaceuticals rule promulgated a new definition of “RCRA-empty” for containers holding hazardous waste pharmaceuticals. If warfarin-based pharmaceuticals are in a unit-dose container (e.g., unit-dose packet, cup, wrapper, blister pack), §266.507(a) notes that the container is RCRA-empty and the residues are not regulated as hazardous waste provided the pharmaceuticals have been removed using practices commonly employed to remove materials from that type of container (e.g., all pills have been removed). Thus, for containers that once held nonacute warfarin-based pharmaceuticals to be considered empty, it will not be necessary to measure the remaining contents. For containers that once held acute warfarin-based pharmaceuticals to be considered empty, it will not be necessary to triple-rinse the containers or demonstrate an equivalent removal method. [84 FR 5905] These empty-container provisions supersede previous agency guidance for warfarin-based pharmaceuticals in RO 14827. [84 FR 5904] If warfarin-based pharmaceuticals are administered via syringe, the RCRA-empty provisions for syringes in §266.507(b) will apply.

Cleanup residue and debris

Section 261.33(d) specifies residues and contaminated soil, water, or debris resulting from cleaning up a P- or U-listed spill are also listed wastes. The regulations refer to spills “into or on any land or water”; however, EPA has stated in guidance that the listings apply to all spill residues, regardless of where the spill occurs. For example, debris from a spill that is contained entirely within a building would be subject to the listings. [RO 13335]

The term “spill debris” has not been defined by EPA, although there was a brief discussion of this issue in the May 19, 1980 Federal Register. [45 FR 33116] The concern expressed by someone in the regulated community was that wrecked rail cars or trucks that had been transporting P- or U-chemicals might be considered to be “spill debris.” The agency stated:

“EPA has chosen not to exclude such debris by definition. If contaminated, these items pose a substantial threat to human health and the environment and should be handled carefully. EPA presumes, however, that in virtually all cases, heavy equipment can be decontaminated and therefore will not become part of the contaminated debris.”

The following examples taken from EPA guidance documents illustrate two issues associated with spill residues.

A warehouse was used to store pesticides that are on the P-list. Wipe tests of the floor and structural I-beams in the building confirm the presence of these chemicals. If the residues resulted from spills of P-chemicals, can a state regulatory agency require cleanup of the warehouse under RCRA?

The spilled materials appear to have been abandoned by accumulating them in the warehouse rather than disposing them elsewhere. They may also have been abandoned by essentially being disposed within the building itself. This makes them solid wastes, and if they were listed P- or U-chemicals, the residues would also be hazardous wastes. If the spills occurred after November 19, 1980 (the effective date of the RCRA regulations), “treatment and containment of spills (except in immediate response to spills) must comply with applicable Part 265 requirements. Since it appears that this is not an immediate response situation, the facility would be subject to an enforcement action for treating, storing, or disposing of hazardous waste without interim status or a permit, and could be required to take appropriate action to clean up the residues.” [RO 11161]

If a manufacturer spills a listed CCP on soil and intends to reclaim the spill residue, is it listed hazardous waste?

If a spill residue can be returned to a process or otherwise put to beneficial use, it would not be a listed hazardous waste. However, the burden of proof is on the generator to show that legitimate recycling will take place. “In the absence of strong, objective indicators of recycling or intent to recycle a spill residue, ‘the materials are solid wastes immediately upon being spilled because they have been abandoned’ (November 22, 1989; 54 FR 48494) and must be managed in accordance with all applicable RCRA standards.” [RO 13743] More discussion of recycling spilled products can be found in Section 14.3.7.

What does “technical grades of the chemical” mean?

As stated earlier, CCPs include “technical grades of the chemical.” Here is how EPA defines technical grades of a chemical:

“The Office of Solid Waste uses a definition of technical grade which is in general usage by the chemical profession. Technical grade refers to all commercial grades of a chemical, which in some cases, may be marketed in various stages of purity. There are no exact criteria, such as percent purity, to define technical grade of a substance. The technical purity of a chemical substance will vary from compound to compound and may range from highly purified to very impure.” [RO 11348]

“Potentially, ‘technical grade’ or ‘commercially pure grade’ can refer to any and all grades of purity of a chemical that are marketed, or that are recognized in general usage by the chemical industry.” [RO 11521]

What is a “sole active ingredient”?

If a chemical product is not pure (i.e., it is a mixture of several chemicals), it can still be a listed hazardous waste when discarded if the product has only one active ingredient and that ingredient is on the P- or U-list. EPA defines an active ingredient as a chemically active ingredient that performs the primary function of the product. [RO 11348, 11350, 11405, 14686, 14820, 14850] For example, a pesticide product might consist of a mixture of several chemicals; however, if only one of the chemicals kills bugs, it is the sole active ingredient. If that chemical is on the P- or U-list, the pesticide is that listed waste when disposed in its unused form. Fillers, solvents, surfactants, propellants, colorants, preservatives, etc. are considered to be inert, nonactive ingredients.

If a product to be discarded has more than one active ingredient, it would not be a P- or U-listed waste per the federal RCRA regs, even if all active ingredients are on the P- or U-list. There is one possible exception to this rule: EPA cites an example of a pesticide that contains chlordane (U036) and small amounts of heptachlor (P059). Both of these chemicals kill bugs; hence, under the guidance cited above, the pesticide should not be P- or U-listed when disposed. When EPA evaluated this product, however, it found that heptachlor is an impurity produced in the synthesis of chlordane that cannot be extracted economically (i.e., heptachlor is not mixed with chlordane to produce the product). Under these circumstances, EPA decided that the product had a sole active ingredient (chlordane) and would be U036 if disposed. [RO 11348]

A product contains two active ingredients, only one of which is on the P- or U-list. Is the product a listed hazardous waste when disposed?

No. “It is not necessary for a chemical to be listed in §261.33(e) or (f) in order to meet the definition of an active ingredient…. If a formulation has more than one active ingredient, the formulation, when discarded, would not be within the scope of the listing in §261.33, regardless of whether only one or both active ingredients are listed.” [RO 13530]

A laboratory either buys P- or U-listed CCPs to use directly as quality assurance (QA) standards, or it synthesizes the standards by diluting them with water, acidic/basic solutions, organic solvents, or an inert media (such as soil) to the appropriate concentration levels. Each of the standards contains a single P- or U-chemical. If excess quantities of these unused standards are disposed, are they listed hazardous wastes?

“Yes. Dilution of a commercial chemical product is not considered use of a commercial chemical product in this case. Thus, the excess QA standards intended for disposal would be listed hazardous wastes under §261.33.” [RO 11437; see also RO 11523] This answer holds true even if the solvents used to dissolve the CCP are themselves listed in §261.33. [RO 11523]

A QA solution consisting of aldrin (P004) and dieldrin (P037) dissolved in methanol will be disposed. What waste code should be applied to the excess solution?

Because the solution contains more than one active ingredient, neither the P004 nor the P037 waste codes would apply. When a solvent is used to formulate a compound or product, it does not meet the listing description for spent solvents; therefore, the F003 waste code is also not appropriate. Because the solution would probably exhibit the ignitability characteristic, D001 is the most likely waste code for the excess solution. [RO 11523]

Paint stripper contains methylene chloride, toluene, and other inert materials. Is the unused stripper a listed CCP when disposed?

The answer in this case depends entirely on which ingredients are active when removing paint. If only the methylene chloride is active, it would be U080. If only the toluene is active, it would be U220. If both are active, the unused stripper would be hazardous only if it exhibits a characteristic. [RO 11787] See also RO 14686.

Manufacturing process wastes

When asked why manufacturing process wastes containing P- and U-chemicals aren’t considered to be P- or U-wastes, EPA provided the following rationale:

“Manufacturing process wastes…generally contain only low levels of these materials. Thus, expanding the hazardous waste identification regulations to encompass all manufacturing wastes containing the §261.33 compounds is likely to result in many false positives (i.e., wastes identified as hazardous which do not actually contain hazardous levels of the toxicants of concern) unless, and until, minimum concentration thresholds can be established for each compound. At this time, due to the lack of data, the agency is unable to set thresholds for all the compounds.” [RO 11026, 12024]

A manufacturing facility has a release of “wet toluene” (i.e., toluene that contains 5% water) from a storage tank. How is this release regulated?

If the toluene is unused, it could be off-spec CCP, and the release would be U220. However, if the toluene picked up the water during use in a manufacturing process, it is a manufacturing process waste that would be considered a “spent material.” Depending on how the toluene was used in the process, it could be F005 spent solvent, or it could be an unlisted manufacturing process waste that is hazardous only if it exhibits a characteristic. [RO 14194]

Manufacturing or product handling?

Sometimes, the issue of what constitutes a manufacturing process waste can become quite complex. In guidance, EPA has decided that “a point exists in the manufacturing process in which an operator creates either a commercial chemical product or manufacturing intermediates. When these chemicals meet a listing description under §261.33, any discard of these materials (including these materials captured on filters or mixed with other wastes) are considered hazardous wastes and must be handled accordingly…. Process wastes are generated prior to the creation of the product or intermediate and may be listed as F- or K-wastes under EPA’s listing system.” [RO 14095]

Let’s start with manufacturing processes. Chemicals on the P- and U-list are often used as raw materials to make products; these products could be in the form of bulk materials. Wastes generated from storing or transferring the P- or U-chemicals before they enter the first step of the manufacturing process will carry the applicable P- or U-codes. Conversely, wastes generated during manufacturing operations where the P- or U-listed chemicals are being used are manufacturing process wastes—not P- or U-wastes. This concept is illustrated in the top diagram in Figure 1 and by the following example.

Figure 1

Diethylhexyl phthalate (DEHP) is used to manufacture small capacitors. Rags, gloves, and other miscellaneous solid materials absorb DEHP (which is listed as U028) during the manufacturing operations. Are these materials listed hazardous wastes when disposed?

If the contamination results from using these materials during the manufacturing process (e.g., gloves become contaminated as a result of handling materials during manufacturing), they are not listed U-wastes. Note, however, that if the materials become contaminated when cleaning up spills or leaks of unused DEHP, such as from the DEHP raw material storage tank or transfer line, they would be U028 when disposed. [RO 12423]

What some facilities might consider to be “manufacturing,” however, is simply “product handling” in EPA’s eyes. Consider a drug company that purchases warfarin (P001) from a manufacturer and then packages the chemical into tablets of different strength. The tablets contain warfarin as a sole active ingredient at concentrations between 0.45% and 4.5%. It would seem logical that the drug company is producing the tablets in a manufacturing process, and that residues from the process would be considered manufacturing process wastes, not P001. The residues in question, all of which contain low concentrations of warfarin, include the following:

  • Washdown water from cleaning machinery, containers, implements, and manufacturing rooms;
  • Disposable gloves, gowns, and other personal protective equipment used by employees in the manufacturing area; and
  • Airborne dust that is collected in air filters, which are periodically discarded.

EPA decided that such materials generated from manufacturing operations prior to the point where a CCP is produced would be manufacturing process wastes that are not covered by the §261.33 listing. In other words, the original warfarin manufacturer might generate these process wastes and not manage them as P- or U-wastes. However, the agency determined that the drug company is simply handling a CCP that has already been produced; that is, they are involved in product handling and do not have manufacturing process wastes. Therefore, all of the wastes noted above that are produced at the packaging facility would be listed hazardous wastes (see the bottom diagram of Figure 1). The washdown water would be P- or U-listed, but might be eligible for the de minimis loss exemption of §261.3(a)(2)(iv)(D). The personal protective equipment and air filters are listed debris because they “contain” warfarin. [RO 14095]

In a similar example, a company repackages toluene (U220) and methylene chloride (U080). Cartridge filters are used to remove dirt and other solids from these products during unloading, transfer, and packaging. When the filter cartridges become dirty or when there is a product change, they are flushed with water and discarded. The washed filters contain small amounts of the U-listed chemicals. As in the previous example, EPA decided that, because the filters contain U-chemicals that have already been produced (i.e., they already meet a listing description in §261.33) but are being discarded, they must be managed as U-listed hazardous waste. [RO 11325]

Once again, please note that in each of these examples, the materials being handled are already CCPs and are simply being repackaged.

Unreacted reagent from reactors

Personnel at chemical plants sometimes ask about the regulatory status of unreacted reagents that exit manufacturing process units (e.g., reactor vessels). If the reagents are on the P- or U-list of commercial chemical products, would unreacted chemicals exiting reactor vessels still carry the P- or U-code if disposed?

The agency first addressed this issue in preamble language as follows:

“We also note that leftover, unreacted raw materials from a process are not spent materials, since they never have been used.” [January 4, 1985; 50 FR 624]

This language would imply that, if they never have been used, they are still products and would carry the P- or U-codes if discarded.

Subsequent to that preamble discussion, EPA issued a letter noting that:

“the term ‘commercial chemical product’ refers to a substance manufactured for commercial use which is commercially pure or a technical grade and formulations in which the chemical is the sole active ingredient. It does not refer to a material, such as a process waste, that contains any of the substances listed in §261.33(e) or (f).” [RO 11076]

EPA also issued three guidance letters to chemical companies [RO 11079, 11326, 12809], discussing the regulatory status of unreacted solvents exiting a manufacturing system, where the solvent was used as a reactant to manufacture a chemical product. In every case, the agency noted that the excess solvent exiting the reactor would not be a listed spent solvent, because it was used as a reactant—not just as a reaction (synthesis) media. EPA noted in one letter that the excess solvent would not carry the associated U-code. In the second letter, the agency noted that the unreacted waste stream would not be listed. In the final letter, EPA said that the chemical company would be responsible for determining whether the unreacted waste stream exhibits a characteristic (implying that it would not be listed).

Based on the sum of the guidance available, we believe that once a chemical leaves its raw material storage area and crosses the manufacturing process boundary to any type of processing equipment, it has been used (see the top diagram in Figure 1). Otherwise, all manufacturing process wastes would carry U-codes whenever a U-chemical was used as a feedstock, and this clearly is not the case in RCRA. See also RO 12004 and 14194.

The unreacted reagent stream could be hazardous by K-listing or if it exhibits a characteristic.


Topic: Toxicity

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