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ENVIRONMENTAL HAZARDS - INSPECT, TEST, REMEDY
ACCURACY vs PRECISION of MEASUREMENTS
AIR CLEANER PURIFIER TYPES
AIR FILTERS for HVAC SYSTEMS
AIR FILTERS, OPTIMUM INDOOR
AIR FILTERING STRATEGIES
AIR HANDLER / BLOWER UNITS
AIR LEAK DETECTION TOOLS
AIR LEAK SEALING PROCEDURE
AIR POLLUTANTS, COMMON INDOOR
AIR QUALITY IMPROVEMENT STRATEGIES
AIR TEST FOR MOLD: ACCURACY
AIR TEST SAMPLING CASSETTE STUDY
AIRBORNE PARTICLE ANALYSIS METHODS
AIRBORNE MOLD SPORE COUNT ACCURACY
ALLERGEN TESTS for BUILDINGS
ANIMAL ALLERGENS / PET DANDER
ANIMAL ENTRY POINTS in BUILDINGS
ANIMAL ODORS IN BUILDINGS
ASBESTOS IDENTIFICATION IN BUILDINGS
ASBESTOS MATERIAL REGULATIONS
ASBESTOS REMOVAL GUIDE, FLOORING
ASBESTOS RISK ASSESSMENT
ATTORNEYS and EXPERT WITNESSES
BACKDRAFTING HEATING EQUIPMENT
BIBLIOGAPHY for ENVIRONMENTAL HEALTH, MOLD, IAQ
BIOGAS PRODUCTION & USE
BLACK MOLD, HARMLESS COSMETIC
BLACK MOLD, TOXIC & ALLERGENIC
BLEACHING MOLD, Advice about
BOD WASTEWATER TEST
BOOK MOLD, Moldy Book Cleaning
BOOKSTORE - ENVIRONMENTAL
BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING
BLUE vs YELLOW COMBUSTION FLAMES
BUILDING SAFETY HAZARDS GUIDE
Cadmium in the home
CAR MOLD CONTAMINATION
CARBON DIOXIDE - CO2
CARBON MONOXIDE - CO
Carbon Nanotube Hazards
CACTUS FUNGI / MOLD
CARPET DUST IDENTIFICATION
CARPET MOLD CONTAMINATION
CARPET TEST PROCEDURE
CARPETING & INDOOR AIR QUALITY
CAT DANDER in BUILDINGS
Cell phone Radiation Hazards
CERAMIC TILE, ASBESTOS in?
CHIMNEY INSPECTION DIAGNOSIS REPAIR
CHEMICAL CONTAMINANTS in WATER
CHINESE DRYWALL HAZARDS
CHLORINE IN DRINKING WATER
CHLORINE IN SEPTIC WASTEWATER
COMBUSTION GASES & PARTICLE HAZARDS
COMBUSTION PRODUCTS & IAQ
CONDENSATION or SWEATING PIPES, TANKS
CPSC Indoor Air Pollution Book Online Copy
DIRECTORY of MOLD / ENVIRONMENTAL EXPERTS
DIRT FLOOR MOLD CONTAMINATION
Disinfecting Buildings with Bleach
DRAFT HOODS - gas fired
DRAFT MEASUREMENT, CHIMNEYS & FLUES
DRAFT REGULATORS, DAMPERS, BOOSTERS
Diethylstilbestrol - DES
DUCT SYSTEM & DUCT DEFECTS
DUST ANALYSIS for FIBERGLASS
DUST SAMPLING PROCEDURE
EMERGENCY RESPONSE, IAQ, GAS, MOLD
EMF Cancer Scare
EMF RF FIELD & FREQUENCY DEFINITIONS
EMF ELECTROMAGNETIC FIELDS & HUMAN EXPOSURE
EMF Levels of Cancer Risk
EMF MEASUREMENT INSTRUMENTS
EMF MEASUREMENT PROCEDURES
EMF SURVEY PROCEDURE - Details
EMF WORKSHEET for EMF MEASUREMENTS
EMF WORKSHEET Example
EMF WORKPLACE EXPOSURE
ENVIRO-SCARE - PUBLIC FEAR CYCLES
FEAR of MOLD - MYCOPHOBIA
Fiberboard Insulation Sheathing Mold
FIBERGLASS INSULATION MOLD
FIBERGLASS PARTICLE CONTAMINATION TEST
FIBERGLASS INSULATION MOLD
FIBERGLASS PARTICLE CONTAMINATION TEST
FIRE DAMAGE vs MOLD DAMAGE
Fireplaces & Woodstove Contaminants
FLAME COLOR, BLUE vs YELLOW COMBUSTION
FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP
FLOODS IN BUILDINGS-mold
FLOOR DAMAGE DIAGNOSIS
FLOOR & SUBFLOOR MOLD, HIDDEN
FLOOR TILE ASBESTOS IDENTIFICATION
FLOOR TILE HISTORY & INGREDIENTS
FUNGICIDAL SPRAY & SEALANT USE GUIDE
GAS DETECTION INSTRUMENTS
GAS EXPOSURE EFFECTS, TOXIC
GAS EXPOSURE LIMITS & STANDARDS
GAS TEST PROCEDURES
GAS FIRED WATER HEATERS
GAS LP & Natural Gas Safety Hazards
GAS PIPING, VALVES, CONTROLS
GLARE, Sunlight/Lighting Control
HEAT LOSS in BUILDINGS
HEAT LOSS DETECTION TOOLS
HEATING OIL EXPOSURE HAZARDS, LIMITS
HEATING OIL PIPING TROUBLES
HEATING OIL SLUDGE
HEATING OIL TANKS
HOUSE DUST ANALYSIS
HOUSEWRAP AIR & VAPOR BARRIERS
HIDDEN MOLD, HOW TO FIND
HOME HEATING SAFETY
HUMIDITY CONTROL & TARGETS INDOORS
INDOOR AIR QUALITY & HOUSE TIGHTNESS
INDOOR AIR QUALITY IMPROVEMENT GUIDE
INDOOR AIR QUALITY METHODS COMPARED
INSULATION INSPECTION & IMPROVEMENT
INSULATION IDENTIFICATION GUIDE
INSULATION, UFFI UREA FORMALDEHYDE FOAM
ITCHY FABRICS, DIAGNOSE
LAB & FIELD IAQ EQUIPMENT SOP
LAB PROCEDURES MICROSCOPE TECHNIQUES
LEAD POISONING HAZARDS GUIDE
LEAD CONTAMINATION in WATER, HOW to TEST
LEAD EXPOSURE HAZARDS INDOORS
LEAD IN DRINKING WATER, HOW to REDUCE
LEAD PAINT REMOVAL ALTERNATIVES
LEAD PIPES in BUILDINGS
LEAD in ROOFING, EFFECTS
LEAD TEST KIT for HOME USE
LEAD in WATER, ACTION LEVEL & REMEDIES
LEED GREEN BUILDING CERTIFICATION
LEED Building Designation & IAQ
Legionella Legionnaires' Disease
Legionella BACTERIA & HVAC Equipment
LIGHT, GUIDE to FORENSIC USE
LP & Natural Gas Safety Hazards
METHANE GAS SOURCES
MILDEW REMOVAL & PREVENTION
MOISTURE CONTROL in BUILDINGS
MOLD: A COMPLETE GUIDE TO MOLD
MSDS Material Safety Data Sheets
MVOCs & MOLDY MUSTY ODORS
MYCOPHOBIA, STAINS MISTAKEN for MOLD
MYCOTOXIN EFFECTS of MOLD EXPOSURE
Museum Artifact Preservation
NOISE / SOUND DIAGNOSIS & CURE
ODORS GASES SMELLS, DIAGNOSIS & CURE
OIL, HEATING, EXPOSURE HAZARDS, LIMITS
OIL HEAT ODORS
OIL SPILL CLEANUP / PREVENTION
OIL TANK LEAK ODORS
OIL TANKS INSPECT LEAK TEST ABANDON REGS
OXYGEN - O2
OZONE for MOLD OR ODORS
PAINTS & COATINGS ODORS IN BUILDINGS
PARTICLE SIZES & IAQ
Particulates & Allergens Indoors
Pesticide Exposure Hazards
PET ALLERGENS / PET DANDER
PET STAINS on FLOORS
PET STAINS on WALLS
PLASTIC CONTAINERS, TANKS, TYPES
PLASTIC HEATER VENT
PLASTIC ODORS-SCREENS, SIDING
PLUMBING SYSTEM ODORS
PVC - VINYL BUILDING PRODUCTS
RADON HAZARD TESTS & MITIGATION
SAFETY HAZARDS GUIDE
SAFETY HAZARDS & INSPECTIONS
SEPTIC METHANE GAS
SEPTIC SYSTEM ODORS
SEWAGE BACKUP TEST & CLEANUP
SEWAGE & SEPTIC CONTAMINANTS
SEWAGE CONTAMINATION in BUILDINGS
SEWAGE PATHOGENS in SEPTIC SLUDGE
SEWER GAS ODORS
SICK HOUSE IAQ QUESTIONNAIRE
SIDING, ASBESTOS FIBER CEMENT
SMELL PATCH TEST to Track Down Odors
SOUND CONTROL in BUILDINGS
STAIN DIAGNOSIS on BUILDING EXTERIORS
STAIN DIAGNOSIS on BUILDING INTERIORS
SULPHUR & SEWER GAS SMELL SOURCES
THERMAL TRACKING Indicates Heat Loss
UFFI UREA FORMALDEHYDE FOAM INSULATION
URETHANE FOAM Deterioration, Outgassing
VAPOR BARRIERS & CONDENSATION in BUILDINGS
VAPOR BARRIERS & HOUSEWRAP
VAPOR CONDENSATION & BUILDING SHEATHING
VENTILATION in BUILDINGS
VINYL CHLORIDE HEALTH INFO
VINYL Siding or PLASTIC Window ODORS
Volatile Organic Compounds VOCs
WATER ODORS, CAUSE CURE
WATER TESTS, CONTAMINANTS, TREATMENT
WATER TEST CHOICES & WATER TEST FEES
WATER TREATMENT EQUIPMENT CHOICES
WIND TURBINES & LIGHTNING
World Trade Center Collapse Dust Photos
This paper discusses electromagnetic radiation or electromagnetic fields (EMF) as a possible cancer risk and offers a brief analysis of the probable cancer risk from EMF compared with other hazards.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
What is an Electromagnetic Field (EMF) or Electromagnetic Radiation (EMR)
Our page top illustration graphs the effect of fear of power lines and EMF exposure as well as other environmental concerns as it affects property values over time.
We define "Enviro-Scare" (ES) and we use this cyclic fear pattern to describe the variation and effects of the level of public environmental worry by recapping the enviro-scare history of asbestos, EMF, UFFI, and other environmental concerns. The red graph depicts the varying level of ES or public fear for a given environmental concern. ES generally increases, peaks, and then diminishes over time, independently of the actual level of risk.
As people become acclimated to the particular topic it loses its initial shock value.
Every (electric) current going through a wire generates magnetic radiation which travels around the wire. There is continuing controversy regarding possible health effects of exposure to this radiation.
The U.S. Environmental Protection Agency (EPA) and the U.S. Navy performed a study which reported that 5 out of 6 laboratories found increased levels of embryological changes in chickens when exposed to magnetic radiation.
Other tests have shown biological effects on mice, miniature pigs, and humans. Recent articles claim or at least suspect that exposure to high levels of ELF radiation is a factor in leukemia in children. A recent article in The New Yorker Magazine along with other media reports have focused public attention on this topic.
Magnetic radiation surveys measure Extremely Low Frequency (ELF) and Very Low Frequency (VLF) fields which have nothing to do with high frequency radioactivity such as radon, X-rays, and so-called ionizing radiation. In a separate article we report on several recent studies and articles which discuss the health issues regarding ELF and VLF radiation.
Magnetic radiation is produced by high tension power lines, but also by ordinary secondary lines, power transformers, household wiring, certain electric radiant heating devices, improperly grounded appliances.
For details about electromagnetic field hazard assessment see the articles listed at page top or at Related Topics .
Frequently Asked Questions (FAQs)
Questions & answers or comments about the cycle of pubic anxiety surrounding potential or actual environmental hazards.
Ask a Question or Enter Search Terms in the InspectApedia search box just below.
Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
We coined the term "Enviro-Scare" in the 1980's to describe the cyclic growth then decline of consumer fear about various environmental issues. As I indicated at the introduction, the graph depicts the varying level of public fear or "Enviro-Scare" for a given environmental concern. This pattern also occurs for many other public anxieties.
"Enviro-scare" generally increases, peaks, and then diminishes over time. The level of fear in an enviro-scare curve is mapped on the chart's vertical axis, increasing from the chart bottom towards its top. Time is mapped on the horizontal axis, increasing from left to right.
The phases of the enviro-scare cycle: increasing fear, peak fear, and declining fear map the curve's up-slope, peak, and declining slope. This behavior can be represented by a normal curve. At its right end the curve approaches zero (no fear) but never quite reaches it.
Predictability: The level of Enviro-Scare (ES), or consumer concern, moves in a predictable pattern: increasing fear, peak, then declining fear. What is significant is that the level of public fear follows this pattern based on mediate attention and a public perception of risk, rather than on the actual risk of a particular hazard.
Thus both genuinely dangerous conditions and those which are really insignificant both follow the ES cycle. This pattern of human response to frightening conditions has been documented in other fields, such as public fear of crime waves, and in another form, public enthusiasm for particular products - the "Dutch Tulip Mania" at the turn of the last century or the "pet rock" come to mind.
The two colors and two different curve slopes in the illustration here simply portray two different enviro-scare topics, one of which increases faster and reaches a higher level of concern than another.
Having worked with building owners and buyers for quite some time, we have personally observed the "enviro-scare" cycle across a variety of environmental hazards, some real and important and some at least eventually considered probably insignificant. The statements below about the current level of enviro-scare on each topic discussed are simply the author's opinion based on contact with home owners, buyers, and Building inspectors in U.S. More scientific surveys could certainly be designed and conducted.
Here is a summary of the actual health risks and property value risks associated with UFFI or urea formaldehyde foam insulation. See Urea Formaldehyde Foam Insulation UFFI for details about UFFI insulation.
This foam insulation was a popular insulation retrofit product used in the 1970's. As an expanding foam insulation it was mixed on-site and pumped into building wall or other cavities in older buildings which were not previously insulated.
Some research suggested that formaldehyde out gassing from the insulation formed a significant cancer risk. The level of formaldehyde that out gassed from UFFI depended in part on how the foam product was mixed at the site, and not all building insulation projects using this substance produced the same level of formaldehyde.
Eventually, additional study suggested that the initial cancer risk from formaldehyde was not supported, at least in this application.
More interesting to me was the observation that perhaps largely because this insulation formed an open-celled foam, even if there were high initial formaldehyde out gassing levels, after months or at most a few years, even careful measurements were unable to detect any levels of ongoing formaldehyde out gassing from this material.
Only people hypersensitive to chemicals seem to have any remaining reaction to this material, and even in that case a study of such reactions is complicated by the observation that higher levels of formaldehyde out gassing from building products occurs from some furniture padding and from some glues or finishes used in chipboard based cabinets or sub flooring.
Yet at the peak of the UFFI enviro-scare, and exacerbated by inconsistent advice offered by government and private health experts, some buildings were sold at a significant discount to allow for extensive gutting, cleaning, and re-insulating of building cavities. Inspecting several such projects it was interesting to note that the one real defect of this insulation product was that depending on how it was mixed, it shrank after installation, leaving gaps of no actual insulation at the top and sides of wall cavities - it wasn't the perfect insulating seal that was promised, but it was not the carcinogen that was feared.
The current level of public fear of UFFI is quite low, but because some people are either hyper sensitive to chemicals in their environment, or because others have a very high level of concern for any environmental or possible environmental issue, consumer concern for this issue has not fallen to zero. See Urea Formaldehyde Foam Insulation UFFI for details about UFFI insulation.
Enviro-Scare about Asbestos in buildings: asbestos pipe insulation in buildings and asbestosis, & asbestos cement building siding
Here is a summary of the health risks and property value risks associated with exposure to asbestos in buildings.
There is no doubt that exposure to high levels of airborne asbestos has been demonstrated to be a serious health hazard (John Mansville's class action lawsuit).
At the peak of the asbestos enviro-scare, very costly asbestos abatement projects were performed. After many cases of inadvertent cross-contamination of building areas by asbestos stirred-up during removal, a careful discipline for asbestos abatement was developed as well as training and licensing requirements.
Current "best-advice" for asbestos pipe insulation in buildings is to leave it alone unless it is in poor condition (falling off) or it is in a location subject to mechanical damage and release in an occupied area. That's because it was discovered that the asbestos level in buildings was worse from it being disturbed than if it were left alone. The current level of public enviro-scare about asbestos has diminished significantly, but as with UFFI, not to zero.
See IDENTIFICATION of ASBESTOS in buildings for details about the visual identification of asbestos-containing materials in buildings.
Cement asbestos shingles are a cementious material, not friable, and unlikely to release a measurable level of fibers into the air around a building unless the siding is being attacked with power tools such as saws, sanders, or during actual building demolition.
If, however, demolition of this material is planned, some communities may require special handling and special disposal, adding to the remodeling or demolition cost. For this reason some owners simply install new siding atop the old, burying it in the building where it is not visible and where it will not be damaged by other building activities.
More advice about asbestos cement building siding as well as its repair or replacement with fiber cement shingles that do not contain asbestos can be read at ASBESTOS CEMENT SIDING.
Who pays for building inspections and environmental tests:
When a building is being purchased, the responsibility for identifying (testing for) and planning to deal with asbestos materials in a building usually rests with the building buyer, as it should: the buyer needs to be absolutely sure that any inspections or tests on a building, including the home inspection, are done by a person with no conflicts of interest.
In some transactions the ultimate cost of tests may be negotiated between the buyer and seller, but if the buyer hires and pays for the inspector, all parties, seller, buyer, realtors, attorneys, are protected from a possible conflict of interest and fear of biased or careless inspecting and reporting.
For a thorough discussion of radon hazards in buildings, radon exposure risk levels, cancer risks for radon in air or water, radon measurement advice, and how to mitigate a high indoor radon level, see RADON HAZARD TESTS & MITIGATION
Radon, a radioactive but odorless and colorless gas occurs naturally in the soil in some areas. Radon has been associated with lung cancer among people exposed to high levels such as those working in mines.
This data was extrapolated to suggest a possible lung cancer risk if radon reached high levels in residential buildings, into which it might seep from soils below.
Because the radon level in a building varies widely over time, the US EPA suggested that homes with radon above 4 picocuries per liter (pCi/L) based on a short term (typically 4-day) test should perform additional longer-term study to see what the actual annual average exposure is. Here's where things got sticky.
Some homeowners are employed by companies requiring that they move to a new city from time to time. Some such employees are offered relocation assistance including the purchase of their present home so as to free-up their investment to purchase a new property. Independent "relocation companies" formed to handle this transaction and to actually carry the older home in their property inventory until it could be sold.
Because the relocation companies didn't want to risk discovering that they were holding a high-radon home that might require a $2000-$2500 (typically) repair, these firms took the position that any home (being offered to the relocation plan service) having a screening-test radon level of 4 pCi/L (or above) must be remediated before they would accept the property.
This position converted the EPA's recommendation for further testing into a requirement that thousands of homes at or close to 4 pCi/L of radon must be remediated. The actual risk to a building occupant from radon at this level is practically nil. Put it this way: if you breathe radon-contaminated air at 4 pCi/L for 18 hours a day for 70 years, then if you get lung cancer at the end of that period, only then, at that exposure level, could you say that the radon may have caused the lung cancer. Contracting lung cancer before then would be indistinguishable from the general risk level in the population.
Now to be fair, radon risk increases exponentially at higher levels, and is perhaps 80 times greater for people who smoke cigarettes. But in effect, thousands of homes were "remediated" at a level of radon of or close to 4 pCi/L without having demonstrated an actual health risk. The current level of public enviro-scare about radon is low but not zero, most-likely because of increased familiarity with the issues and because the remediation cost is less than for UFFI and asbestos.
For a thorough discussion of radon hazards in buildings, radon exposure risk levels, cancer risks for radon in air or water, radon measurement advice, and how to mitigate a high indoor radon level, see
Enviro-Scare about Lead in building Paint or Water Supply Piping and Neurological or other health risks
How Serious is the Environmental Hazard from Lead in Paint
Lead in paint is likely to be a real risk in buildings, especially to children. The actual risk depends on the dose: the actual level of lead consumed. Building conditions which increase the risk of lead paint ingestion include the location of surfaces where lead paint was used, the condition of the surface, activities which release lead-dust such as certain types of cleaning, sliding window sashes up and down, and building renovation work.
Lead was used as paint in buildings in the U.S. up to 1978, so unless a pre-1978 building has no painted surfaces it's reasonable to assume that lead paint is present. Thus superficial testing for the "presence/absence" of lead paint is not a step I'd recommend, though for appropriate cases I do recommend a lead survey by a qualified expert.
Lead enviro-scare has generated an industry selling "lead tests" for paint, often based on rather unreliable chemical swabs. A trained expert, using an x-ray inferometer, can sample the appropriate building surfaces at a property and will prepare a document describing the important risks and should prepare a lead abatement plan if action is needed. Some U.S. states such as Massachusetts require lead abatement in buildings at the time of property transfer.
Because any pre-1978 painted building is likely to have lead paint on some surfaces, homes for sale and with this enviro-scare hazard are not particularly stigmatized (from a property valuation concern for lead paint) since most homes of similar age have the same paint concerns. The result is a flatter enviro-scare curve, with its right-hand tail leveling out higher above zero. The current level of enviro-scare about lead in paint is moderate and probably stable.
See LEAD TEST KIT for HOME USE for a simple test kit for lead on building surfaces, pottery, toys, etc.
How Serious is the Environmental Hazard from Lead in Water
Sources of lead in drinking water include several items:
The current level of enviro-scare about lead in water piping is moderate and probably stable.
The current level of enviro-scare about EMF exposure is quite low but not zero, as with asbestos and UFFI. We discuss this topic in depth at Electromagnetic Field Measurement Procedures.
For details about electromagnetic field hazard assessment see these articles:
Also see EMF RF FIELD & FREQUENCY DEFINITIONS for a simple explanation of different types of radio frequency (RF) and electromagnetic frequency (EMF) types and where they are found.
We have had more to say on this and on mycophobia than should be repeated here. There are both legitimate and imagined hazards associated with mold and allergens in buildings. For full details about the sources, effects, and costs of fear of mold, both justified and exaggerated, please see Mold Enviro-Scare.
Public concern with "black mold" is perhaps confusing since some of the most problematic molds in buildings are not dark in color and in fact can be a bit difficult to see (Aspergillus sp. and Penicillium sp. for example.)
Readers should see The Mold Information Center: What to Do About Mold in buildings, When and How to Inspect for Mold, Clean Up Mold, or Avoid Mold Problems. The toxic or "black mold" enviro-scare level is currently past the peak of consumer concern but is no less than mid-slope on the declining side of the curve.
The enviro-scare curve for this topic appears to be flatter and more drawn-out than the topics listed above. As with the electromagnetic field EMF cancer risk topic discussed above, there are various parties with conflicting interests, all sponsoring research on this topic.
Our own field investigations find that fiberglass particles are quite common in indoor air. Unless the forensic particle laboratory is making a point of counting small fiberglass fragments in indoor air or dust samples, only a large-particle count may be provided and the presence and potential effects of fiberglass dust may be underestimated. Furthermore, proper lab procedure and use of mountants with an appropriate refractive index to see glass fragments is critical as otherwise such particles may simply be invisible when viewed using conventional slide preparation methods.
Some research argues that fiberglass particles are larger than and less dangerous than asbestos. However many small fiberglass particles may be in indoor air but may be below the threshold of some common measurement methods. See FIBERGLASS HAZARDS in buildings.
For more information about fiberglass as an indoor air quality concern see:
Phases of Enviro-Scare and Effects on Real Estate & Property Values Due to Public Fear of Environmental Hazards
If a building owner wants to sell the property, the impact of the presence of an environmental issue on the real estate transaction depends on the time, or point in the fear cycle, at which the property is being marketed.
The time until a property moves from phase I to phase II is extremely difficult to predict. However it may be easier to detect phase III, the beginning of decline in consumer fear.
Properties on the "up-slope" of the ES curve, phase II, face declining market value or increasing time on the market unless a price adjustment is made.
The opposite is true of properties on the "down-slope" or phases III and IV. This concept may be useful in advising home buyers and sellers concerning the economic impact of the presence of various controversial health or environmental issues at a given property.