Protecting and Training Workers in Mold Remediation and Maintenance | Fungus of the month: Botrytis
By Dave Gallup
In May of this year, the National Clearinghouse for Worker Safety and Health Training published a 35 page document entitled Guidelines for the Protection and Training of Workers Engaged in Maintenance and Remediation Work Associated with Mold. These guidelines were the product of two workshops in January and June of 2004 in which over 60 technical experts convened and discussed the training and protection requirements that should be put in place to protect those who remediate mold. The stated purpose of the document is to develop "experience-based guidelines for protecting and training mold assessors, mold remediation workers, and workers exposed to mold in the course of maintaining building systems". It is a well written, organized and easily understood set of guidelines. Note that the guidelines specifically do not apply to single unit, owner-occupied residential housing units. Nor does it apply to the training necessary to effectively perform mold assessments or remediation. It is clearly focused upon the health and protection of the workers mentioned above. It is also clear in stating that this is intended to be a "living" document that will need revision as our understanding of mold improves.
The guidelines begin by breaking the training audience into two groups, "maintenance" and "remediation" which are carefully defined. Mold assessors and consultants are felt to be part of the "maintenance" group for training purposes because it is assumed that if mold assessors meet the AIHA-LAP, LLC qualifications for this competency, they will already have had substantial training and experience with mold and safety.
The document proposes that the following four factors should be considered in determining mold exposure potential:
It is proposed that training should include public, office, multi-family and commercial buildings but, again, not single family residences. It is suggested that training for those in the "maintenance" group should be a maximum of two hours. Suggested training times for "remediation" workers is 21 hours, with some dissention about the latter timeframe specifically cited within the guidelines. Both of these suggested times can be modified based upon an individual's prior training and demonstrated competency.
The guidelines note that there are no OSHA standards and, consequently, they relied upon the wealth of prior recommendations made by various groups including the ACGIH, AIHA-LAP LLC, ASTM, Health Canada, IICRC, NADCA, NYC DOH, OSHA, and the US EPA. From these groups they pull recommended training topics for maintenance and remediation workers engaged in general mold work and HVAC system work. They also generate a table summarizing recommended worker protection in the same activities. Also included is a table from the US EPA with recommended response guidelines to clean water damage to prevent mold growth.
The Guidelines may be downloaded at http://www.wetp.org by clicking on the "Mold Guideline Link"
The US EPAs guidelines for response to clean water damage may be found at https://www.epa.gov/mold
By Griselda Hernandez
Members of the genus Botrytis are ubiquitous in the environment and have been found worldwide. They are commonly found in indoor environments and have been isolated from many substrates including carpets, mattress dust, paper, floors, and wallboard. Although not typically considered to be soil-borne, Botrytis has been isolated from different types of soil and sand.
Botrytis species are sensitive to humidity changes. Under high humidity conditions, water is absorbed causing the intracellular pressure to increase and eventually rupture, thereby releasing spores into the air. This is known as hygroscopic spore dispersal. In outdoor settings or greenhouses, large numbers of spores are dispersed by rain or water splash. Botrytis spores are found relatively commonly in spore trap and culture samples and are easily identified. They are recovered in the highest numbers in the spring, where they are recovered approximately 30% of the time and least frequently in the fall with a recovery rate of approximately 10%. When recovered, the spore density is relatively low, with the 50th percentile value being only about 20 to 25 spores per cubic meter.
Figure 1: Botrytis frequency of detection and spore density by month.
The gray bars represent the frequency of detection, from 0 to 1 (1=100%), graphed against the left axis. The red, green, and purple lines represent the 2.5, 50, and 97.5 percentile airborne spore densities, when recovered, graphed against the right hand axis. (Source: EMLab™ MoldRANGE™ data. Total sample size for this graph: 39,878.)
Botrytis spores are generally hyaline (with a tear-drop shape and a rather thick cell wall that can be easily seen). To the untrained eye, the spores can resemble basidiospores due to a prominent scar where they were attached to short denticles on their conidiophores (spore-producing structures) however, Botrytis spores are much larger and more symmetrically shaped. When recovered in culture media, the fungus has a very distinct grayish color and can be identified easily among other fungal colonies. One distinctive characteristic of Botrytis is the production of sclerotia, which are large, dark-colored resting structures consisting of compacted hyphae (fungal body) that can be seen with the naked eye as dark brown to black dots. Sclerotia are wintering or "resting" structures that allow the fungus to withstand adverse environmental conditions. These structures, under favorable conditions, may give rise to mycelium (hyphal mass) or fruiting bodies that allow Botrytis to reestablish itself.
Fig 2: Microscopic photograph of Botrytis species
It is well documented that Botrytis is especially abundant in temperate or subtropical regions where humidity is relatively high. However, spores and resting structures (sclerotia) have been known to survive long periods of low humidity. Germination will be triggered once humidity increases.
Once established, Botrytis survives as a saprobe or parasite. As a saprobe, Botrytis mainly obtains its nutrients from non-living organic matter. When living as a parasite, it is capable of colonizing a wide range of host plants.
Botrytis is commonly known as "gray-mold" due to the color changes it undergoes as it rapidly invades decaying plant tissue. Its growth commences as a colorless (hyaline) mass and gradually turns a light gray to dark brown with age. Botrytis is of economic concern because it can infect a variety of ornamental and crop plants such as cabbage, lettuce, carrots, onions, shallots, flax and legumes. Soft fruits such as strawberries and grapes are also susceptible to Botrytis infection. In addition, research has shown that some species may be seed-borne in some host plants which can make them vulnerable to infection. However, not all Botrytis infection is considered to be damaging. In the wine making industry, grapes are purposely infected with Botrytis creating "noble rot". The grapes are allowed to over-ripen on the vine and when they eventually crack open Botrytis will colonize the fruit, facilitating a decrease in water content and an increase in sugar concentration.
This article was originally published on August 2005.