I was thinking that it would be good to have a topic dedicated to some research and science articles to better understand the many facets of roof cleaning. Topics including the chemicals used, governmental articles,biology, health related articles etc.
Here are a few that I found pretty interesting.
Excerpt from http://www.tnenvis.nic.in/Lichens/LichenFAQ.pdf
Q. How do lichens break down rock to make soil? A. First of all, it takes a very long time for a lichen to break down a rock, but, this does happen and can be witnessed by studying rocks of various ages in volcanic regions. Lichens and mosses are the first colonizers after a volcanic eruption. Many lichens contain acids that help break down rock. Furthermore, the mechanical action of the fungal threads of the lichen penetrating the spaces between the rock crystals together with changes in temperature and moisture also help break down rock into soil.
This helps us explain why the shingles or tile roofs could be compromised but also gives a general understanding of what we are removing to better explain with an educated response to customers questions.
This article from the CDC explains: Cynobacterial Blooms and HABs While I would never ever inference any medical advice to homeowner and some have used the article by Morganroth as an educational tool, this might serve a similar purpose. As well as maybe one more reason to use that respirator while working on the roof. As we really do not have any way to detect if they might be the HAB type. Erring on the side of caution. One other thought is this article can be utilized, against claims that insist pressure washing a roof being superior for the enviroment. Being that we nor they, have the ability to detect what is growing on the roof, it should only be used as informational and no conclusions displayed. If there are HABs on the roof would a customer want them blown into their environment by a pressure washer?
Excerpts from http://www.cdc.gov/hab/cyanobacteria/about.htm 1) Humans can be exposed to cyanobacterial toxins by drinking water that contains the toxins, swimming in water that contains high concentrations of cyanobacterial cells, or breathing air that contains cyanobacterial cells or toxins (while watering a lawn with contaminated water, for example). 2) In Australia, where cyanobacteria are prevalent and CyanoHAB-related poisonings are well-documented, health officials have set up intensive monitoring systems and have written guidelines for public-health response to CyanoHABs. Similar, less-intensive monitoring systems exist in the Lake Champlain Basin area of North America, and in states such as Maryland and Florida.
Full CDC reports on Cyanobacteria http://www.cdc.gov/hab/cyanobacteria/default.htm
(Really sorry about the link problem, I am going to try my other computer to see if the problem is my system. )
KIM R
-- Edited by Presidential Pressure Washing on Tuesday 23rd of November 2010 05:08:20 PM
Has the federal government made recommendations to protect human health?
EPA established an environmental air limit of 0.5 ppm. Exposure to higher levels could result in discomfort and irritation. Dependent on the concentration, these effects may be reversible when exposure ends.
OSHA set a legal limit of 1 ppm chlorine in air as a ceiling limit. At no time should a worker's exposure exceed this limit.
EPA established a maximum contaminant level (MCL) and maximum residual disinfectant level (MRDL) of 4 mg/L for free chlorine in drinking water.
WHAT EPA PROGRAM OFFICES REGULATE CHLORINE, AND UNDER WHAT LAWS IS IT REGULATED? __________________________________________________________________________ EPA OFFICE LAW PHONE NUMBER __________________________________________________________________________ Pollution Prevention Toxic Substances Control Act (202) 554-1404 & Toxics Emergency Planning and Community Right-to-Know Act (EPCRA) Regulations (Sec. 313) (800) 424-9346 Toxics Release Inventory data (202) 260-1531 Air Clean Air Act (919) 541-0888 Solid Waste & Comprehensive Environmental Emergency Response Response, Compensation, and Liability Act (Superfund)/ Resource Conservation and Recovery Act / EPCRA (Sec. 304/311/312) (800) 424-9346 Water Clean Water Act (202) 260-7588
A technical support document can be requested from the TSCA Assistance Information Service, (202) 554-1404.