Archive for the ‘Biocides’ Category


One of the more famous quotes from William Shakespeare’s play, Romeo and Juliet.

Language Matters

In this month’s article I’ll address the use of what I call unregistered microbicides.

Over the course of the past several decades, industry and regulators have taken increasingly jaundiced views of chemical substances variously known as antimicrobial pesticides, biocidal substances, biocides, biocidal products, and microbicides. What are these substances? The EU’s Biocidal Products Regulation (BPR – Regulation (EU) No 528/2012 of the European Parliament and of the Council of 22 May 2012) Article 3, 1 (a) offers this definition:

any substance or mixture, in the form in which it is supplied to the user, consisting of, containing or generating one or more active substances, with the intention of destroying, deterring, rendering harmless, preventing the action of, or otherwise exerting a controlling effect on, any harmful organism by any means other than mere physical or mechanical action,

any substance or mixture, generated from substances or mixtures which do not themselves fall under the first indent, to be used with the intention of destroying, deterring, rendering harmless, preventing the action of, or otherwise exerting a controlling effect on, any harmful organism by any means other than mere physical or mechanical action.

A treated article that has a primary biocidal function shall be considered a biocidal product.

I’ve highlighted key words in the BPR definition because one response from industry has been to replace products that are registered as microbicides with alternative chemistries that do are not registered. They then promote their finish goods as being “biocide free.”

I pose this question:
Is it legitimate to make a biocide-free claim if a substance is used to control microbial contamination in a formulated product although it does not have an antimicrobial pesticide registration?

Non-biocidal additives in water-miscible metalwork fluids (MWF)

There are three groups of products related to MWF biodeterioration resistance – bioresistant, biostatic, and adjuvant additives.

Bioresistant additives

Bioresistant (recalcitrant) additives are chemistries that are difficult for microbes to use as food. As illustrated in Figure 1, their concentration in a fluid is unaffected by the fluid’s bioburden.

Fig 1. Bioresistant MWF additive – additive concentration is unaffected by microbial load (bioburden).1

Biostatic additives

In contrast to bioresistant additives, for which there appears to be no interaction between microbes and the additive, biostatic additives contribute to the MWF formulation’s ability to resist microbial growth. Figure 2a shows that when a biostatic MWF is inoculated with microbes, they do not proliferate (i.e., the biobuden does not increase). However (Figure 2b), if a biostatic additive is added to a heavily contaminated MWF, it has no effect on the biobuden.

Fig 2. Biostatic MWF additive – a) When microbes are added to biostatic MWF formulation, they do not proliferate; b) when a biostatic additive is added to a heavily contaminated MWF, it has no impact on the bioburden.


Additives that have no direct impact on microbial contamination in MWF (Figure 3a), but which improve the performance of microbicides are called adjuvants. Figure 3 illustrates this concept. Microbicides can kill off microbes (Figures 3b and 3c, red line), prevent microbes from proliferating (Figure 3d), or do both.

Fig 3. Adjuvant MWF additive impact on biomass – a) adjuvant without microbicide; b) microbicide speed of kill without adjuvant; c) microbicide speed of kill with adjuvant; d) microbial proliferation in MWF formulated with microbicide (red line) and microbicide plus adjuvant (purple line).

Similarly, an adjuvant can increase a microbicide’s speed of kill (Figure 3c, purple line), prolong the duration of its effectiveness against repeated challenges (Figure 3d, purple line) or both. The red arrows in Figure 3d indicate weekly inoculation of the test MWF with a microbial challenge population per ASTM Practice E2275.

Unregistered, microbicidal additives in water-miscible MWF

A key word in BPR’s biocide definition is intention. With this word, BPR’s definition shifts from an objective perspective – if a substance has a controlling effect on microbes, it is a microbicide – to a subjective perspective – only if it was intended for a substance to have a controlling effect on microbes is that substance subject to BPR registration. The U.S. Federal Insecticide, Rodenticide and Pesticide Act (FIFRA) has similar language (Sec. 2 [17 U.S.C. 136 (u)). The challenge is in reaching consensus on the meaning intention regarding the use of MWF functional additives.

Functional additives

In the MWF sector, a functional additive is a chemical substance that provides one or more performance properties to the fished formulation. Typical functional additive performance properties include:

  • Corrosion inhibition
  • Coupling – additives that provide chemical bonds between dissimilar substances (e.g., base oils and polar molecules)
  • Emulsion stabilization
  • Foam inhibition
  • Lubricity
  • Microbicidal activity
  • pH control (buffering)

Products used in several of these functional categories also impact microbial contamination. All chemicals sold for use in technical applications Europe must be registered in accordance with Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH – Regulation (EC) No 1907/2006 of the European Parliament and of the Council of 18 December 2006). In the early and mid-1990s, I was hopeful that REACH would the toxicity data required for all industrial chemicals would be similar. This would have closed the cost gap associated with obtaining the toxicity data needed for microbicide registration versus that needed for non-microbicidal substances. However, requiring a full toxicological test package for each of the millions of industrial chemicals was determined to be prohibitively expensive. Additionally, the time and laboratory facilities required to test all industrial chemicals rendered the concept untenable. Consequently, although some toxicological data are required to support product registrations under REACH, substantially more is needed for product registration under BPR. This creates a grey zone.

What is the difference between a registered and an unregistered microbicide?

Per the definition I quoted in the opening paragraph, a registered microbicide is an active substance (ingredient) or formulated product intentionally used to control microbial contamination and approved for such use by the cognizant regulatory agency (e.g., the European Chemical Agency’s – ECHA’s – Biocidal Products Committee, and the U.S. EPA’s Office of Pesticide Programs).

There is no consensus on definition of an unregistered microbicide. Nor is there consensus about the concept of intention. There is no universally agreed upon demarcation between a non-biocidal additive that also affects microbial contamination and one that has some level of non-biocidal activity (e.g., corrosion inhibition) but primarily inhibits microbial growth. To further complicate matters, there are numerous technical grade substances that are substantially more toxic than biocidal products. Moreover, there are registered microbicides that have non-biocidal applications. For example, hexahydro-1,3,5-tris(hydroxyethyl)-s-triazine (HTHT – CAS 4719-04-4) is registered as a MWF microbicide under the BPR, FIFRA and other nations’ pesticide regulations. However, it is also an effective sulfide scavenger used to scrub sulfide from gas generate during petroleum refining. When the product is sold for antimicrobial purposes, it has a pesticide label. When it is sold as a sulfide scavenger it has a technical chemical, it has a substantially less informative label – there is no intention of antimicrobial activity when HTHT is used as a sulfide scavenger.

For decades, I have argued the following:

  • If an additive demonstrates one or more, better than average, non-biocidal functional properties – regardless of its antimicrobial properties – it need not be registered as a biocidal substance unless biocidal claims are made.
  • If an additive does not demonstrate one or more, better than average, non-biocidal functional properties, and demonstrates antimicrobial performance, it should be registered as a biocidal substance.

Case study – Dicyclohexylamine

Dicyclohexylamine (DCHA, CAS 101-83-7) is a secondary amine that has been used in MWF formulations for more than two decades. As a chemical group, amines have several performance properties, the most common of which are:

  • Corrosion inhibition
  • Emulsion stabilization
  • pH control (buffering)

However, performance in each category varies substantially among amines. When DCHA has been tested for its corrosion inhibition, emulsion stabilization, or pH control performance, it has not compared favorably relative to other amines. Figure 4 is a plot of DCHA’s antimicrobial performance in a MWF. Testing was performed per ASTM Practice E2275. As Figure 4 illustrates, in a MWF that contained DCHA at 3,000 mg kg-1 (ppm), the challenge population fell to below detection levels (BDL) and remained BDL for the duration of the eight-week study.

DCHA is an example of a chemical that has demonstrated antimicrobial performance properties, is represented as having typical amine performance properties (although with no supporting data) and is used in MWF formulations. It is a prime example of an additive that does not demonstrate one or more, better than average, non-biocidal functional properties, and demonstrates antimicrobial performance – i.e., an unregistered microbicide.

Fig 4. ASTM Practice E2275 test results – MWF formulated with DCHA at 3,000 mg kg-1.

Now compare DCHA’s toxicity profile with that of HTHT. The data in Table 1 are taken from the products’ respective Safety Data Sheets (SDS). Per the SDS data, DCHA’s acute oral toxicity is >5x that of HTHT and its acute dermal toxicity is 10x that of HTHT. Moreover, DCHA’s ecotoxicity is greater than that of HTHT and its biodegradability is less than that of HTHT. Consequently, although MWF formulated with DCHA can claim to be biocide-free (they do not contain appropriately registered microbicides), they are potentially more toxic and less environmentally acceptable.

Table 1. Product SDS toxicity profile comparison – DCHA and HTHT.

Are there regulatory or liability issues?

This is an issue for regulators and lawyers. I am neither. However, there are precedents that suggest MWF compounders who use putative performance additives that do not actually demonstrate one or more, better than average, non-biocidal functional properties, but do demonstrate antimicrobial performance have exposure on both counts. There have been class-action lawsuits in which the plaintiffs have claimed adverse health effects caused by MWF exposure and in which MWF compounders have been listed as defendants. One can only speculate on the impact of formulations with unregistered microbicides on the ability of formulators to create a credible defense against adverse health complaints.

From a regulatory perspective, the issue is what claims are made. Some years ago, a food grade lubricant compounder formulated some of their products with PARABENs (para-hydroxy benzoic acid esters). Although PARABENs are commonly used as food and cosmetic preservatives, they are not registered as industrial microbicides. The compounder promoted the antimicrobial activity of their food grade lubricant. In doing so, they violated two laws. They used unregistered biocidal products as microbicides in the lubricant. They made pesticidal claims for their lubricant, although the product did not have a U.S. EPA pesticide registration. The compounder was quite fortunate in that the US EPA OPP did not press criminal charges and the fine was a fraction of what it might have been, had the US EPA’s officials applied the standard $5,000 per incident (i.e., each customer site at which product was used) per day. It has been argued that if a compounder does not claim microbial contamination resistance or other antimicrobial performance properties in their written literature, they will not come under the US EPA’s OPP scrutiny. I wonder if the risk is worth the benefit.

In terms of antimicrobial pesticides, the MWF sector is an orphan the total MWF microbicide market is estimated to be <$200 million U.S.). With the continued consolidation of biocide manufactures, and increased cost of providing all of the toxicological test data needed to support new microbicide registrations, the only new microbicides likely to be made available for use in MWF are active ingredients that have been approved in non-MWF, large volume (i.e., >$50 million opportunity for a given product) markets.


What does the term “biocide-free” mean if MWF formulated with chemistries that are more toxic than the appropriately registered antimicrobial pesticides that they replace? I suggest that all stakeholders from compounders to end-users are safer if they use additives for which complete toxicological profiles are available rather than alternatives for which only limited data are available. The increased amount of information provided on microbicide labels doesn’t make them more hazardous than other industrial chemicals. Just as a rose by any other name is would smell as sweet, a microbicidal chemical – unregistered microbicide – by any other name is just as toxic – perhaps even more so.

As always, I look forward to receiving your questions and comments at

1 I originally created Figures 1, 2, and 3 for STLE’s MWF 240 Metalworking Fluid Formulation Concepts course, Module 3 Minimizing MWF Biodeterioration Risk.


John Cleese and Michael Palin of Monty Python’s Flying Circus in the “Dead Parrot Sketch”, first aired in December 1969.
What is a dead microbe and why might we care?

I today’s post, I’m returning to a topic I first discussed in 2019 ( In the Monty Python’s Flying Circus “Dead Parrot Sketch”, John Cleese plays the role of an unhappy customer who believes that he has just purchased a dead parrot. Michael Palin – playing the shopkeeper – insists that the parrot is not dead. Rather, it is “simply napping.”

When we monitor microbial contamination in industrial systems, we are typically interested in both how much microbial contamination is present and what damage risk the population poses to the system and the fluids it contains.

Last week, I received an email from a metalworking fluid (MWF) manager who wrote: ““We have another situation with dormant bacteria. In this case we find we have to keep hitting it with biocide more and more often. When the bacteria do start to grow again as the biocide level drops, we see huge pH, alkalinity drops within a week and there is often a bad smell associated. I worry that this is partially due to a large population of dormant bacteria (104 CFU mL-1 to 105 CFU mL-1 on paddles) that is able to wake up and grow more quickly. Is there a way to get at these bacteria and kill them to reduce their population?”

With the MWF manager’s approval, today’s article draws heavily on my response to his email.

Dormant cells

Bacterial endospores

Endospores are special structures formed by a few types of bacteria. Endospores are metabolically inactive (i.e., dormant). There have been reports of microbiologists inducing endospores that have been dormant for more than a million years to germinate into vegetative (i.e., metabolically active) cells. Until recently (i.e., the past ~ 15 years), microbiologists believed that only endospore-forming microbes like Bacillus sp. (Gram +, spore-forming aerobic rods) and Clostridium sp. (Gram +, spore-forming anaerobic rods), could survive for long periods in a dormant – metabolically inactive state (Figure 1).

Fig 1.
Fig 1. Bacterial endospores – a) Bacillus subtilis; b) Clostridium tetani. In these photomicrographs, the B. subtilis endospores appear as green spheroids and the C. tetani endospores appear as blue spheroids (sources: a); b)


Persister Cells

In the late 1980s, microbiologists started to report on the existence of persister cells – non-sporeformers that seemed to be able to withstand biocide treatment. In some respects, persister cells are like trees that are dormant during the winter but become active as spring arrives. When conditions are unfavorable, these cells become metabolically inactive and can remain in this state for thousands of years. Unlike endospore-forming bacteria, persister cells do not form any special structures.

Understanding of persister cells grew as biofilm research advanced. It turned out that persister cells were often resistant to biocide treatment because they were metabolically inactive – much like endospores but without the unique endospore cell wall chemistry. Thus, the study of persister cells evolved into the study of dormant cells. Thus, the terms persister and dormant are used to describe cells that can become metabolically during tough times and then become active after prolonged periods (1,000s of years) of inactivity. The biology of dormancy and reactivation is still a hot research topic.

Viable but not culturable (VBNC) cells

The rapid development of non-culture microbiological test methods, starting with protein concentration testing in the 1940s, ATP testing in the 1950s, and rudimentary genomic testing in the 1970s (my lab used to test seawater samples for total DNA concentration among other microbiological parameters), led to an awareness that not all microbes were readily detected by culture methods. In 1982, a ground-breaking study focused on a disconnect between the incidence of cholera disease among Chesapeake Bay area restaurant patrons and the inability of the local Department of Public Health to recover the bacterium Vibrio cholera form suspect oyster meat. A post-doctoral fellow at the University of Maryland decided to compare microscope direct counts with culture data. He came of with the idea of treating specimens with a reagent that prevented cell division but permitted cell growth. Metabolically active V. cholera cells would show up as >10x their normal size. Dormant and moribund cells would be visible as normal sized cells. Low and behold, shellfish samples that yielded no culturable V. cholera actually had 106 to 109 metabolically active – i.e., quite viable cells mL-1! That work precipitated an avalanche of research on VBNC microbes.

The term VBNC includes two distinct categories of microbes.

Injured cells – The first category includes cells like the aforementioned V. cholerae that sometimes can be cultured but not reliably. These normally culturable cells are unable to reproduce on or in the growth medium that was designed to detect them if they are injured. Since the early 1980s, process steps have been added to culture test to help injured cells recover before they are cultured for enumeration.

Most types of bacteria – The second category includes microbe we do not yet know how to culture. They do not product colonies on any of the available growth media, under commonly used growth conditions (i.e., temperature, oxygen availability, etc.). Current estimates suggest that for every organism that has been successfully cultured, 1 million to 1 billion that exist in nature have not been cultured.

Metalworking Fluid Microbial Contamination Condition Monitoring

Choosing one or more test methods

If you test a population of people for height and weight you will find that – generally speaking – people’s weight increases with their height (Figure 2a). However, the relationship falls within a cloud around the trendline. Contrast this with the relationship between refractive index (°Brix) and metalworking fluid concentration ([MWF]) shown in Figure 2b. The trend lines in both graphs have the same slope, but the data point spread around the trend line is much greater for the height versus weight plot than it is for the °Brix versus [MWF] plot.


Fig 2. Correlations between pairs of parameters – a) human height versus weight (a significant, but weak correlation); b) refractive index (°Brix) versus [MWF] (significant and strong correlation).


I’ve discussed this concept in previous What’s New posts (see,, and

The relationships among different microbiological test methods reflects the fact, that like Figure 2a, above, each method measures a different property (see

Each test method tells a story

Between the dormant cell and VBNC cell factors, there are quite a few reasons that culture and non-culture testmethods can tell different stories. In some cases, culture data suggest a greater biodeterioration risk than actually exists (i.e., substantial bioburdens are not damaging the MWF). In others, culture data suggest that there is negligible biodeterioration risk but other data – such as ATP – indicate that the biodeterioration risk is great. This happens when a substantial portion of the metabolically active population is either non-culturable or clumped into masses (flocs) of cells and each such mass (100s to 1000s of cells) forms a single colony. So how do we interpret apparently conflicting data from two different methods. I’ll use culture (CFU mL-1) and cellular ATP concentration ([cATP] in pg mL-1) to illustrate the concepts.

When culture testing indicates high bioburden, but ATP data does not – if the population is dormant in the MWF but becomes metabolically active after being transferred to a growth medium, the population represents a potential risk. It is not causing damage at present, but could become metabolically active at some future point, as I will discuss below. As illustrated in Figure 3, the biodeterioration risk is moderate.

When culture testing indicates low bioburden, but ATP data indicates high bioburden – if a substantial percentage of the population is VNBC but metabolically active, it represents a current risk. Even though culture recoveries are minimal, the population is using MWF components as food and is producing acids and other metabolites that can degrade MWF performance. Per Figure 3, the biodeterioration risk is high.

It should be obvious that when both culture and ATP-bioburdens are low, the biodeterioration risk is low. Conversely, when both culture and ATP-bioburdens are high, the biodeterioration risk is high.


Fig 3. Biodeterioration risks based on culture and ATP-bioburden data.


Assessing microbicide performance in MWF systems

Based on the preceding background discussion, if microbicide treatments are not having the desired effect, it is important to assess whether the population in the treated MWF is dormant populations or not. because of the MWF dynamics, the available biocide concentration rapidly decreases to less than the critical (i.e., minimum effective) concentration with sufficient speed that bioburdens seem to yo-yo quickly (see the August 2018 What’s New article for an explanation of critical microbicide concentration).

For example, in a system with 10 % turnover per day, fluid loss through turnover rate will drop 2000 ppm biocide to 1,180 ppm in five-days. Add to that biological demand (microbicide consumption as it kills microbes) and chemical demand (microbicide reactions with other organic compounds in the MWF, dissolved metals, and salts, causing the microbicide molecule to either breakdown or become biologically unavailable) and it is easy to see how the concentration of biologically active microbicide can fall to below its critical concentration (1,000 ppm for triazine) within 4 to 5 days.

Dealing with rapidly restored bioburdens

Case 1 – Culturability is affected but [cATP] is not – If the population drops shortly after biocide addition, then the biocide is effective when it is present in the >critical concentration range. If you have a field test for microbicide concentration ([microbicide]), you can do a quick trial to track [cATP], CFU mL-1, and [microbicide] before treatment and at 8h to 12h intervals post-treatment. If the treatment is effective, within 24h the [cATP] should drop by ³2 orders of magnitude. Determine the [microbicide] at which [cATP] begins to climb and the number of days post-treatment it takes for that to happen.

Figure 4 illustrates Case 1. Initial treatment causes both CFU mL-1 and [cATP] to drop as expected. This indicates that the microbicide is effective at recommended end-use concentration. However, over time, both [microbicide] and CFU mL-1 show a seesaw pattern. As the [microbicide] decreases, CFU mL-1 increases. The [cATP] remains unaffected. This indicates that even at 750 mg L-1 (ppm), the microbicide is working as a biostat – keeping most of the population dormant.


Fig 4. Microbicide effect on bioburden – Case 1.


Case 2 – [cATP] is affected but culturability is not – In this case, the CFU mL-1 is not affected by microbicide dosing. However, there is an inverse relationship between [cATP] and [microbicide]. The [cATP] initially drops in response to 2,000 mg L-1 microbicide dosing but recovers as the [microbicide] falls. Regardless of the [microbicide] the CFU mL-1 remain within the test method’s (paddles) normal variability range (±1 order of magnitude). Figure 5 illustrates Case 2.


Fig 5. Microbicide effect on bioburden – Case 2.


Case 3 – [cATP] and culturability are affected – In this scenario, illustrated in Figure 6, microbicide treatment causes both parameters to fall. As the [microbicide] decreases, both culturable and ATP-bioburdens recover. Note that after a microbicide addition, the impact on CFU mL-1 is faster than the effect on [cATP]. This is because cell injuries are likely to inhibit culturability almost immediately after treatment. However, it takes longer for cells to actually die. A full effective microbicide treatment will produce data similar to that shown inf figure 6. Keep in mind that Figures 4, 5 and 6 all pertain to a high-turnover system in which dilution is the primary factor affecting the microbicide’s half-life. That said, in systems with low turnover rates (< 5 % per day), the patterns will be similar but the x-axis will stretch out.

Fig 5. Microbicide effect on bioburden – Case 3.

Sorting out the three cases

AxP testing – AxP testing uses ASTM Test Method E2694 for Measurement of Adenosine Triphosphate in Water-Miscible Metalworking Fluids to obtain extracts that include ATP, adenosine diphosphate (ADP), and adenosine monophosphate (AMP). The “x” in AxP is used to indicate that the method tests for all three molecules. Recently, Drs. Peter Küenzi, Jordan Schmidt, and I collaborated to asses the relationship between MWF additives and Adenylate Energy Charge – AEC (see The AxP data are used to compute AEC. Dormant or moribund populations have AEC <0.5. Healthy populations have AEC ³0.7.

Per the preceding discussion of VBNC and dormant cells, high AEC with low CFU mL-1 signals the presence of an active but non-culturable population. Conversely, high CFU mL-1 and low AEC signals that the microbes recovered by culture testing are not causing damage in the MWF. They are either dormant or dying off, but able to recover in the growth medium. I do not recommend AxP for routine testing. It is useful to make seemingly confusing or questionable data make sense.

Test for biofilm growth and biocide effect against biofilms

Commonly, we ignore biofilms (the November 2017 What’s New article discusses biofilms in fuel systems) growing on MWF system surfaces. Research has shown that both the dose needed to disinfect biofilms is typically 10x that used to kill planktonic – free-floating -cells (See December 2019’s What’s New). Additionally, the soak interval – period of contact – must be at least 24h. Biofilms periodically launch cells into the overlying fluid so that they can be transported to new surface colonization sites.

If you do not periodically eliminate biofilm populations, cells from MWF system biofilms readily reinfect the recirculating fluid as soon as the biocide concentration approaches the critical concentration. This is not an issue of dormant cells or VBNC cells. It is simply a reinfection process.

Use the DSA test method to evaluate biofilm accumulation in the system. If your DSA results are ³103 pg cm-2, you will need to do a full system clean out and recharge before you’ll be able to restore reliable bioburden control.


Although culture and ATP data generally tell the story, sometimes they do not.

If the population initially responds to microbicide treatment but recovers quickly, the two most likely causes are:

  • 1. Reinoculation from biofilm communities, and
  • 2. Recovery of the planktonic population when the microbicide’s half-life is shorted faster than assumed.

ATP by both ASTM Test Method E2694 & DSA testing can tell you if Cause 1 is at play. If biofilm growth is causing the data pattern you have reported, you will need to do a drain, clean, and recharge to break the cycle.

ATP, culture, & [microbicide] can tell you if cause 2 is at play. If short half-life is the issue, you’ll have to rethink your dosing plan.

AxP can tell you if there is a dormant population affecting your test results.

For more information, contact me at


How many of you recall the Bob Seeger song: Where have all the flowers gone? It seems that it might be time to modify the lyrics by replacing the word flowers with biocides approved for use in metalworking fluids (MWF). I admit, that’s a mouthful, but the reality is comparable to that behind the original song. The list of active substances for which Biocidal Products Regulation (BPR) dossiers have been submitted includes a mere 27 actives intended for use in MWF. Less than 10 years ago, there were more than 100 options. The dust hasn’t yet settled in the USA, but once the US EPA’s Office of Pesticides Programs rules on the maximum permissible dosage of triazine in MWF later this year, it’s likely that the ASTM E2169, Table 2 list of active ingredients approved for use in MWF will be a fraction of its original length. Perhaps, when compared with our European friends, we are still lucky in the USA. A literal reading of the BPR’s definition of a Biocidal Product suggests that all MWF are Biocidal Products. The UEIL is advocating that MWF be formally recognized as Treated Products (the cost impact is an estimated $250,000 U.S. per MWF formulation – not trivial). Regulators have promised to give UEIL’s arguments full consideration, but nothing has yet been put in writing. I reviewed the latest state of affairs in my January 2016 TAE presentation. Please contact me if you are interested in receiving a copy of the manuscript: Impact of Biocidal Product Regulation on Microbial Contamination Control in Metalworking Fluids.


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