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environment – In Scientio, Veritas

Tag: environment

MSDS (and a bit of Monday morning nerd chuckles)

As every laboratory-based researcher knows, Material Safety Data Sheets (MSDS), nowadays often called simply Safety Data Sheets (SDS)*, are very important as sources of crucial information related to workplace safety and occupational health. These documents, associated individually with every laboratory chemical, contain information on the potential hazards (health, fire, reactivity and environmental) and instructions for safely storing, handling, and working with the said chemical. It also lists emergency procedures to undertake in case of accidental spillage of the material or unprotected exposure to the same.

As one can imagine, these documents, provided by the manufacturers of these materials, are an invaluable resource for formulating reasonable occupational safety and health programs at institutions for scientific research and healthcare in compliance with Federal and State regulatory requirements. The information in MSDSs is targeted towards anyone who works, or comes in contact, with the chemicals, which includes employers, workers, supervisors, healthcare professionals, and emergency responders, including firefighters. Therefore, in order to ensure that MSDS provides the required information quickly and easily, these documents are presented in an easily-readable format and written in a clear, precise and understandable manner, with instructions for looking up further information if necessary. In the US, the Occupational Safety and Health Administration (OSHA) of the Department of Labor determines the Hazard Communication (or “HazCom”) Standard (HCS), which specifies what kind of information must be included on these documents; Canada and European countries have their own similar agencies performing the same function.

So long, the MSDSs were required to have 9 categories of information. However, recently, OSHA has recommended that MSDSs henceforth follow a more comprehensive 16-category format that was established by the American National Standards Institute (ANSI) as a standard for MSDS preparation. According to OSHA:

By following this recommended format, the information of greatest concern to workers is featured at the beginning of the data sheet, including information on chemical composition and first aid measures. More technical information that addresses topics such as the physical and chemical properties of the material and toxicological data appears later in the document. While some of this information (such as ecological information) is not required by the HCS, the 16-section MSDS is becoming the international norm. The 16 sections are: (1) Identification (2) Hazard(s) identification (3) Composition/information on ingredients (4) First-aid measures (5) Fire-fighting measures (6) Accidental release measures (7) Handling and storage (8) Exposure controls/personal protection (9) Physical and chemical properties (10) Stability and reactivity (11) Toxicological information (12) Ecological information (13) Disposal considerations (14) Transport information (15) Regulatory information (16) Other information.

There are many ways to access the MSDS of chemicals. By law, the Health, Safety and Environment (HSE) offices of institutions are required to keep and provide copies of specific MSDSs. However, these documents are now available online also, from the websites of individual manufacturers, as well as from large online databases. Many universities around the world (including my own) have contracted with a chemicals management and MSDS repository system called ChemWatch to provide this information.


Being of a naturally curious bent of mind, I accessed ChemWatch via my institution’s HSE, and did a search for the MSDS for that important laboratory chemical present in various buffers and solutions, namely, Water. You know, water, aqua, agua, ap, paani, H2O, or more popularly, DHMO/dihydrogen monoxide; the same.

The MSDS for Water was largely unremarkable. However, there were some gems in there. A few instances:

Product Identifier
Product name: WATER
Chemical Symbol: H2O
Other means of identification: Not available. Erm… How about ‘visual’? No?
First Aid Measures
Eye/Skin Contact or Ingestion: Generally not applicable. Ahem! ‘Generally’?
Precautions for Safe Handling
Safe handling: Generally not applicable.
Other information: Store away from incompatible materials and foodstuff containers.
Storage incompatibility: None known. Ah! Well then.
Exposure Control/Personal protection
Eye and face protection: Generally not applicable.
Skin protection: See Hand protection below
Hand protection: Generally not applicable.
Body protection: See Other protection below
Other protection: Generally not applicable. I am not kidding. It really does say these.
Basic Physical and Chemical properties
Solubility in water (g/L): Mixes.
Flammability: Not available. Seriously? ‘Not available’?
Information on Toxicological effects
Chronic: Long-term exposure to the product is not thought to produce chronic effects adverse to health (as classified by EC Directives using animal models); nevertheless exposure by all routes should be minimised as a matter of course. Methinks this needs a precise definition of the manner of ‘exposure’.
Skin irritation/corrosion or Eye irritation: Not available. Does ‘shrinkage’ qualify?
Mutagenicity or Carcinogenicity: Not available. How about just ‘No’, or ‘None’?
Ecological information: persistence and degradability
Ingredient: Not available.
Persistence:Water/Soil Not available.
Persistence:Air Not available. Of course not. Stands to reason, right? How can WATER persist in ‘water/soil’ or in ‘air’?

Heh, a rare lazy Monday morning of nerdy fun… [- wide grin! -] I’ll get my coat. KTHXBAI.

* This new short form ‘SDS’… How’d it go with finding the Safety Data Sheet of that ubiquitous molecular biology lab reagent Sodium Dodecyl Sulfate? I am looking for SDS’s SDS. What, a grand-SDS?… I probably shouldn’t quit my day job for improv yet.

It’s anytime-o’clock. Do you know what is growing in your dishwasher?

It may be a jungle out there, but it’s no less a jungle in here as well. Fungal organisms, although technically not plants, are hardy little buggers that are abundant in the environment everywhere, a veritable fungal jungle – even if you can’t always see them. As a group, they can survive almost anywhere – some better than others, of course – under extremes of conditions; they are capable of drawing their nutrition from the soil and dead/decaying organic matter, and can grow on almost any substance, provided there is a degree of moisture (even in form of humidity) present. Many fungi are known to live in symbiotic or parasitic relationships with plants and animals.

Fungal organisms may reproduce and/or disseminate in form of spores. This is most commonly observed in the group of fungi known as molds (variant spelling: moulds). These often have a thread-like (a.k.a. filamentous) body – along, or at the tips of, which they produce single-celled, seed-like spores. Mold spores are reproductive units, highly resilient structures which can survive unfavorable conditions; once formed, they can be dispersed by air currents – even imperceptible disturbances in the air that may be generated by ordinary activities – and may travel great distances by hitching a ride on various surfaces, such as clothing, fur, and so forth. When they eventually settle down on a surface that can sustain fungal growth, they re-grow into the parental form.

Of course, producing spores is not a prerogative of molds only. The other group of fungi, known as yeasts, do that too. While yeasts in general reproduce by budding off daughter cells from a mother cell, under certain conditions they make spores. For instance, the baker’s yeast (Saccharomyces cerevisiae) respond to the condition of nutrient depletion by forming spores, and surrounding each of them by a multi-layered spore wall that confers resistance to various environmental stressors. The disease-causing yeast, Cryptococcus, makes spores both as a result of sexual reproduction, and as a response to nutrient limitations, in either case the ultimate goals being survival, dispersal, and germination into new organisms under conducive conditions.

Did I mention they are resilient? It appears that many, many substances – even seemingly dead, inorganic ones – can sustain the growth of spores in presence of minute quantities of water; all they need is love cellulose, a polysaccharide (or ‘complex sugar’) that is a structural component of the wall of plant cells. Consider the black mold that grows on buildings, inside and out: any plant-derived, cellulose-containing material, such as plywood or regular wood, cardboard, cellophane, paper layers attached to drywalls as backing, carpet fibers, cotton fabric, et cetera can be a haven for the mold spores. Add a little moisture – in form of high humid conditions, water leaks, even moisture build-up via normal breathing and perspiration – and boom! Let there be mold infestation. These molds can also feed on non-dietary, often invisible, organic materials common in households, such as soap, dust particles, and – eww! – shed skin cells trapped in dust, fabric, or carpet fibers.

Fungal organisms generally like slightly warmer temperatures to grow, optimally around 80˚F/27˚C; however, don’t let that fool you. After all, bread mold (often a species of Rhizopus) and mold on cheese (often Penicillium) grow fine at the humid 40-50˚F/4-10˚C of the refrigerator. Yeasts such as species of Cryptococcus are ubiquitous in the non-arid environments of tropical and subtropical countries, with average temperatures ranging between 50-64˚F/10-18˚C. Disease-causing molds (such as Aspergillus) and yeasts (such as Cryptococcus, and pathogenic Candida) grow inside the body at 98.6˚F/37˚C. Under laboratory conditions, on artificial media, yeasts and molds grow at room temperature (generally, 68-77˚F/20-25˚C) or at 95-99˚F/35-37˚C (though sometimes at different rates). I have observed Aspergillus at room temperature on an aqueous solution of a highly alkaline chemical substance (for those who know what it means, it was a pH 9.0 buffer). Fungi, molds and yeasts, have this amazing ability to adapt to their immediate environment, because their enzymes have evolved in such a manner as to remain active over a wide range of external temperatures and chemical conditions.

Nevertheless, in our daily experiences, we have grown used to seeing molds grow – with their fuzzy-wuzzy exteriors – on external surface, more so than the yeasts. Therefore, it may come as a bit of a surprise that a type of thermophilic (high temperature-loving) yeast, called Exophiala dermatidis (a.k.a. the Black Yeast because of its color) – commonly observed in various hot and wet environments, such as the tropical rain forests – should be found on the surface of fruits (such as mango and pineapple) that grow in the tropical climates; in the natural hot water springs in Thailand; humidifiers; Japanese house baths; public Turkish steam baths; and… [drum roll] dishwashers!

Exophiala dermatidis, a related species Exophiala phaeomuriformis, and a mold known as Magnusiomyces capitatus have all been recovered from dishwashers. What is it about dishwashers that makes them such a favorite playground for fungal spores? Scientists surmise that the dishwashers, especially the rubber seals of their doors, may offer a conducive, none-too-harsh environment for spore survival and growth. The internal environment of a dishwasher is rich in organic nutrients in a high pH (alkaline) condition due to regular use of detergents; the temperatures vary intermittently during various cycles, often reaching as high as 60-80˚C, in presence of high humidity arising from processing large volumes of water. High concentrations of salt, used to prevent calcareous accumulations on the inner surface, possibly makes the environment more comfortable for Exophiala, since species of this microbe can grow even at a salt (Sodium Chloride) concentration of 17%, almost 20 times the amount contained in mammalian blood and body fluids.

Wangiella (a.k.a. Exophiala) dermatitidis
Exophiala dermatitidis colony (left) & spores (right);
courtesy: © 2007

In a 2011 study, a group of European investigators sampled 189 dishwashers from various localities in Europe (Slovenia, Austria, Belgium, Croatia, Denmark, Germany, the UK, France, Italy and Spain), South Africa, North America (USA and Canada), South America (Brazil), Israel, Far East Asia (Japan and China), and Australia. The presence of some mold or yeast could be detected in about 62% of these samples; the major culprits were the black yeasts Exophiala, and one white yeast called Candida parapsilosis, followed by low level occurrences of red yeast Rhodotorulla, as well as molds Magnusiomyces and Fusarium – apart from a few other fungi. The researchers made the additional discovery that the hardness of water seemed to play a role in the persistence of the black yeasts in the dishwashers, corroborating earlier evidence that local calcium ion concentrations influenced their growth form and virulence. Not only that, using scanning electron microscopy, they demonstrated that the black yeasts excreted polymeric substances, forming on the rubber seals a tough biofilm within which the microbe was protected from excess heat and mechanical damage.

In a recent study, to be published in July 2013, Turkish investigators sampled 153 dishwashers, in addition to other appliances, from household in the Mediterranean city of Mersin in Turkey, and made similar observations. Almost one in five dishwashers yielded fungi, a whopping 86% of which were the black yeasts, followed by a few white yeast and the mold Magnusiomyces. The researchers also studied the genetic signatures (or genotypes) of these black yeasts, and found that the genotype A appeared to be the most successful in invading urban human habitats and creating a niche for itself in households.

Imagine! Fungal bodies growing, lurking within you dishwasher. In many households, people sometimes leave cleaned utensils, plates and vessels of regular use in the dishwasher for convenience. The implications are astounding!

Earlier studies have demonstrated that high humidity areas in a household, such as kitchens, bathrooms, and steam rooms may offer a haven to fungal organisms, especially those that make sticky spores (in fancy science-y words, “mucuous propagules”), such as the black, white and red yeasts, and the mold Fusarium. Dishwashers may be offering a similar environment within an enclosed, relatively small space.

And why is this important? Well, the potential health hazard, of course. Let’s look at the organisms. Species of Exophiala, earlier known to cause opportunistic lung disease in immune-compromised patients, have been recovered from clinical samples in the US. Magnusiomyces capitatus (alternatively known as Geotrichum capitatum, Dipodascus, Blastoschizomyces or Saprochaete in literature – isn’t fungal taxonomy fun?) has been associated with fatal infections in patients with hematological malignancies, especially leukemia. Both the red yeast, Rhodotorula, and the white yeast, Candida parapsilosis, are clinically significant emerging opportunistic pathogens of debilitated patients, especially those who have indwelling catheters attached for various reasons.

To clarify, there is yet no direct relationship established between dishwashers and human fungal infections. [Note: I am emphasizing this point, because our ever-vigilant Community Manager Khalil brought up an important point in the comments. Cleaning the rubber seals of the dishwasher regularly is an effective deterrent to fungal growth. An acidic solution such as vinegar may help, but the important idea is not to allow moisture to accumulate. If the door is periodically left open, moving air currents are generally effective as a desiccator, which prevents spores from growing. In addition, fungi are ubiquitous in the environment and cannot be avoided; many kitchens, washrooms, boiler-rooms et cetera have yielded similar fungal microbes in the past. Yet, we don’t always fall ill with clockwork regularity, because our immune systems are efficient at combating such external malefactors. As medical science progresses, we have better medications as well to combat such diseases. So… Don’t Panic. no, really. Don’t.]

Nevertheless, it is important to keep in mind that times they are a-changing; both apparently healthy individuals and infirm patients, in today’s world, may have varying degrees of immune suppression due to environmental stressors, disease and/or medical intervention. There is evidence of such an association between mold-infested ‘sick’ buildings and human disease, especially respiratory illness. The recent outbreak of serious meningitis due to medication contaminated by a black mold (Exserohilum rostratum) – traced to poor sterility practices in a Massachusetts pharmacy – was an eye-opener to environmental fungal hazards. Therefore, a continued co-existence with the fungal jungle within one’s own household may one day become a serious public health concern.

UPDATE: An abridged and slightly modified version of this write-up was published in The Conversation UK magazine.

Main Papers cited:

  • Zalar P, Novak M, de Hoog GS, & Gunde-Cimerman N (2011). Dishwashers–a man-made ecological niche accommodating human opportunistic fungal pathogens. Fungal biology, 115 (10), 997-1007 PMID: 21944212
  • Döğen A, Kaplan E, Oksüz Z, Serin MS, Ilkit M, & de Hoog GS (2013). Dishwashers are a major source of human opportunistic yeast-like fungi in indoor environments in Mersin, Turkey. Medical mycology : official publication of the International Society for Human and Animal Mycology, 51 (5), 493-8 PMID: 23167707
  • Horré R, Schaal KP, Siekmeier R, Sterzik B, de Hoog GS, & Schnitzler N (2004). Isolation of fungi, especially Exophiala dermatitidis, in patients suffering from cystic fibrosis. A prospective study. Respiration; international review of thoracic diseases, 71 (4), 360-6 PMID: 15316209
  • Straus DC (2009). Molds, mycotoxins, and sick building syndrome. Toxicology and industrial health, 25 (9-10), 617-35 PMID: 19854820
  • Shoham S, & Marr KA (2013). Treatment of iatrogenic fungal infections: a black mold defines a new gray zone in medicine. Annals of internal medicine, 158 (3), 208-10 PMID: 23147215