HOW THE BILKO INDEX
IS CALCULATED





When you visit this website, you are asked to provide information about the pesticides and cleansers used in your home.   These products (like all matter in the universe) are made up of chemicals, some of which can have toxic effects on people.   In fact, pesticides and cleansers often contain chemicals that are toxic because their purpose is to kill living organisms.

This website will tell you which toxic chemicals are contained in the pesticides and cleansers used in your home.   It will also provide you with your home's Bilko Index, which is a number that reflects the chronic toxicity of your pesticide and cleanser choices.   You will probably find that one or two toxic chemicals are contributing the most to your home's Bilko Index.   Decreasing the use of toxic cleansers and pesticides in your home or switching to less toxic or nontoxic alternatives will result in a lower Bilko Index.   Thus, the Bilko Index provides you with a means for guiding your progress in reducing the use of toxic chemicals in your home.

This website is intended to help you understand toxic chemicals better.   In addition to finding out which toxic chemicals are contained in the pesticides and cleansers that are used in your home, you will learn the extent to which toxicity can vary from one chemical to another.

This part of the website describes how the Bilko Index is calculated.   Your home's Bilko Index depends on five things:

· the types and amounts of cleansers and pesticides that are used,
· the ways in which the cleansers and pesticides are used,
· where the pesticides and cleansers are used (indoors or outdoors),
· the types and amounts of toxic chemicals contained in the cleansers and pesticides that are used, and
· the degree of toxicity of the toxic chemicals contained in the cleansers and pesticides that are used.

An overview of the formula for calculating the Bilko Index, along with the mathematical equation, is given here.

References




Your home’s Bilko Index depends on the types and amounts of cleansers and pesticides used in and around your home:


Pesticides are products that kill weeds, molds, rodents, and insects.   Cleansers include products that clean and deodorize.   The amount of each pesticide and cleanser used in and around your home is one of the factors that decides your home’s Bilko Index.


The values for this part of the Bilko Index calculation come directly from your answers to the website’s survey.


The survey asks which pesticides and cleansers are used in and around your home as well as how much of these pesticides and cleansers are used.   If you know which products are used and in what amounts they are used, the website simply converts the values you provide to units of grams per year.


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The Bilko Index depends on the ways in which pesticides and cleansers are used in and around your home:

There is a wide range of usage patterns for pesticide and cleanser products.   Pesticides and some cleansers are meant to be left in place after application.   On the other hand, some cleansers, such as abrasive products, are meant to be rinsed down the drain immediately after use.   Still others are meant to be applied and then wiped, but not rinsed, off.


The way a product is used in and around the home affects the likelihood of it making contact with people in the home.   As you might expect, products that are left in place after application are more likely to make contact with people in the home than products that are rinsed down the drain.

The product survey asks you to provide information about the way you use each product.  Based on the information you provide, each product’s contribution to your home’s Bilko Index is adjusted by a Usage Factor.  A Usage Factor of 0.01 is assigned to products that are rinsed down the drain immediately after use, while a Usage Factor of 0.1 is assigned to products that are wiped off after use.   Products that are left in place after application are assigned a Usage Factor of one.

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Your home’s Bilko Index depends on where pesticides and cleansers are used (indoors or outdoors):

Most people spend much more time indoors than outdoors.  In fact, the average person spends about twenty times as much time indoors as they do outdoors.  To account for this, the contribution to the Bilko Index for products that are used outside is reduced by a factor of 20. 

Some products are used both indoors and outdoors, and their contribution to the Bilko Index is adjusted proportionately.

Your responses to the website’s survey are used to adjust each product’s contribution to the Bilko Index for indoor and outdoor use by assigning a value called the Place Factor to each product.  The Place Factor is equal to the fraction of product that is used indoors plus one-twentieth of the fraction of the time the product is used outdoors.

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Your home’s Bilko Index depends on the types and amounts of toxic chemicals contained in the cleansers and pesticides used in and around your home:

In this step, the website estimates the amount of each toxic chemical in the pesticides and cleansers used in and around your home each year.   These amounts ultimately depend in part on your answers to the website’s survey, because they depend on how much product is used in addition to the ingredients of the products used and the concentration of any toxic chemicals they contain.


Most of the material in pesticides and cleansers is not toxic.   In fact, the concentration of toxic chemicals in these products tends to be very low.   The active ingredient in a pesticide, for example, usually makes up less than one percent of the total pesticide product.   This means that in a 100 pound bag of a typical pesticide, there is less than one pound of toxic chemical.   The rest of the material is made up of chemicals that are defined as “inactive” ingredients.  They are there to “carry” the active ingredient and make the pesticide easy to apply.  


In some cases, inactive ingredients are fairly toxic chemicals.  However, for pesticides, the active ingredients tend to be by far the most toxic chemicals in the product.  For this reason, only active ingredients are considered when calculating a pesticide’s contribution to a home’s Bilko Index. 


Cleansers that make disinfectant or antibacterial claims are required to register under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA).  The ingredients in these products that are responsible for their antibacterial properties are defined as active ingredients.  Compared to pesticides, however, the “inactive” ingredients in cleansers are more likely to be important contributors towards the product’s overall toxicity.


Unfortunately, reliable and consistent ingredient and concentration data for inactive ingredients in products are difficult to obtain. 


The website’s survey includes a few dozen of the more popular cleanser products.  A comprehensive list of cleansers is impractical because cleanser formulations change frequently and because of the sheer number of cleanser products.  Some of these products are registered under FIFRA, while others do not make disinfectant or antibacterial claims and are not registered.  Information about the inactive ingredients they contain has been extracted from Material Safety Data Sheets (MSDSes) published by their manufacturers, and their contribution to a home’s Bilko Index includes both active ingredients and inactive ingredients reported in the MSDS.


The concentrations of the toxic chemicals contained in pesticides and cleanser products are given here. Separate tables for pesticides and cleansers are given, and each is in alphabetical order by product brand name. These tables also include the manufacturer of each product and its EPA Registration Number, if applicable, and tell what sources of information were used to gather the data.


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Your home’s Bilko Index depends on the degree of toxicity of the toxic chemicals contained in the cleansers and pesticides used in and around your home:

Everything in the world is made up of chemicals, most of which are not toxic.   Water, for example, is a chemical.   Even among chemicals considered to be toxic, there are big differences in toxicity from one chemical to the next.   A small amount of a highly toxic chemical can cause much more harm than a relatively large amount of a less toxic chemical.   Because of this, the Bilko Index depends on the degree of toxicity of the chemicals contained in pesticides and cleansers as much as it depends on amounts used.  

Toxic effects fall into two broad categories:   acute and chronic.   Acute toxicity is a response to a single exposure to a chemical, while chronic toxicity is a response to long periods of exposure or repeated exposures.   Many chemicals can have both acute and chronic toxic effects.   The Bilko Index is intended to reflect chronic health effects only, and potential acute health effects are treated separately.

Chronic effects are divided into two broad categories, cancerous and noncancerous.   Both of these categories are considered when caclulating the Bilko Index.

In addition, there are many routes, or pathways, by which exposure to toxic chemicals can occur.   The primary pathways are ingestion, dermal exposure, and inhalation.   Ingestion of toxic chemicals can occur when pesticides are on food that is eaten, when non-food items are eaten, or when hands that have toxic chemicals on them are put into the mouth.   Some chemicals pass quite readily through skin tissue, creating dermal exposure when they come into contact with skin.   The final major exposure route is inhalation, where chemicals that are breathed into the lungs enter the body.   The extent of a chemical’s toxic effects depends to some extent on the exposure pathway.  

The website calculates a number called the Bilko Dose that provides a measure of the degree of toxicity of each toxic chemical used in the home.   Each toxic chemical has its own Bilko Dose.  When calculating the Bilko Dose, different types of chronic harm that a chemical might cause (cancerous and noncancerous) and different routes, or pathways, through which exposure may occur (by mouth and in the lungs) are taken into account.

The Bilko Dose has units of grams per year.   It is intended to correlate with the amount of a chemical per year over a lifetime that causes chronic toxic effects.  Therefore, highly toxic chemicals that can cause adverse effects even in very small quantities have low Bilko Doses.   Less toxic chemicals have larger Bilko Doses.   The calculation for a chemical’s overall Bilko Dose begins with obtaining a value for ingestion noncancer, inhalation noncancer, ingestion cancer, and inhalation cancer effects.  

The United States Environmental Protection Agency’s (EPA’s) measure of a chemical’s noncancer chronic effects due to ingestion is its oral reference dose, or RfD.   Reference doses are generally given in units of milligram of chemical per kilogram of body weight per day.   The EPA’s corresponding measure of noncancer chronic effects due to inhalation of a chemical is its reference concentration, or RfC.   Reference concentrations are given in terms of concentration, such as parts per million or milligrams per cubic meter.   RfCs and RfDs are generally derived from No Observable Adverse Effect Levels (NOAELs) or a similar value by adjusting them downward, most often by a factor of 100, to account for inaccuracies and assumptions, including the use of animal studies to predict human response, in using studies of short duration, and to conservatively protect sensitive members of a population.

The EPA also assigns potency values for carcinogenic effects.   The risk of cancer due to ingestion of a substance is called its oral slope factor.   Oral slope factors are generally given in units of kilogram-days per milligram and represent the risk to a population of getting cancer from ingesting a milligram of chemical per kilogram of body weight per day over a lifetime.   The risk of cancer due to breathing air that contains a carcinogenic chemical is its inhalation unit risk.   Inhalation unit risk is generally given in units of cubic meter per milligram, which represents the cancer risk to a population of breathing air that is contaminated with one milligram of chemical per cubic meter of air over a lifetime.

A chemical’s RfD or RfC corresponds to a risk of 2.5´10-4 (US EPA, 1999).   In other words, if a population experiences exposure at the level of a chemical’s RfD, 0.025% of the population will experience adverse effects.   This relationship allows chronic noncancer effects to be related to cancerous effects, which are quantified in terms of risk.

Many chemicals that have chronic toxic effects have not been assigned a reference dose, reference concentration, inhalation unit risk, or oral slope factor by the EPA.   The values used for calculating the Bilko Index are taken from Environmental Defense’s Scorecard Risk Assessment Values.   These values are available in comma-delimited format at http://www.scorecard.org/chemical-profiles/def/rav_edf.html.   When RfDs and RfCs are not available, this set of data provides other values, including minimum risk levels (MRLs) from the Agency for Toxic Substances and Disease Registry and recommended exposure limits (RELs) from other agencies.   Like RfDs and RfCs, these values are derived from NOAELs or similar values.   Scorecard also provides cancer risk scores for chemicals that have not been assigned risk scores by the EPA, from sources such as the California EPA’s Office of Environmental Health Hazard Assessment.  

The tier of sources Scorecard uses to select their risk assessment values is given in Table 1.   References and more information on the sources listed in this table is available at http://www.scorecard.org/chemical-profiles/ref/rav_edf.html.

The Ingestion Noncancer Bilko Dose is the oral RfD in milligrams per kilogram per day, divided by 1000 (to convert from milligrams to grams), multiplied by 70 kg (the mass of an average human), and multiplied by 365 (the number of days in a year).   The Inhalation Noncancer Bilko Dose is the RfC in milligrams per cubic meter, divided by 1000 (to convert from milligrams to grams), multiplied by 20 cubic meters per day (the inhalation rate of a 70 kg human), multiplied by 365 (the number of days in a year).   For chemical i, the equations are

and

.

If there is no oral RfD or RfC and an appropriate substitute value is available, then the Ingestion Noncancer Bilko Dose and Inhalation Noncancer Bilko Dose are calculated using the substitute value.  

The Ingestion Cancer Bilko Dose is 70 kg (the mass of an average human), divided by 1000 (to convert from milligrams to grams), multiplied by 365 (the number of days in a year), multiplied by 2.5´10-4 (to convert from risk to dose), and divided by the chemical’s oral slope factor in kilogram-days per milligram.   The Inhalation Cancer Bilko Dose is 20 cubic meters per day (the inhalation rate of a 70 kg human), divided by 1000 (to convert from milligrams to grams), multiplied by 365 (the number of days in a year), multiplied by 2.5´10-4 (to convert from risk to dose), and divided by the inhalation unit risk in cubic meters per milligram.   Formulas for calculating these values for chemical i are:

and

.

As with the noncancer Bilko Doses, if there is no oral slope factor or inhalation unit risk and an appropriate substitute value is available, then the Ingestion Cancer Bilko Dose and the Inhalation Cancer Bilko Dose are calculated using the substitute value.  

As mentioned before, the more toxic a chemical is, the lower its Bilko Dose is, so setting the Bilko Dose for each chemical to the least of the values for the Ingestion Noncancer Bilko Dose, Inhalation Noncancer Bilko Dose, Oral Cancer Bilko Dose, and Inhalation Cancer Bilko Dose ensures that the Bilko Dose (and ultimately the Bilko Index) reflects the most sensitive possibility for exposure pathway and type of effect.   For chemical i, this could be written as

Bilko Dosei = minimum                         {Ingestion Noncancer Bilko Dosei, Inhalation Noncancer Bilko Dosei, Ingestion Cancer Bilko Dosei, Inhalation Cancer Bilko Dosei}.

Table 2 shows the maximum and minimum values for the various toxicity categories of Bilko Doses.   The maximums and minimums shown here were calculated from values for more than a thousand chemicals (not necessarily found in pesticides and cleansers) in the Scorecard database (this does not include Scorecard’s Risk Assessment Values for radionuclides).   As shown in this table, Bilko Doses for chemicals with an assigned Risk Assessment Value range over ten orders of magnitude, from 2.6´ 10-8 grams per year for TCDD, the most toxic chemical, to 6.6´ 102 grams per year for FREON 113, the least toxic chemical.

Table 2 also shows the range of Bilko Doses for a set of 36 high-volume residential pesticides and/or cleansers that have been identified as priority health and safety threats (US EPA,   1999; WestP2Net, not dated, a and b).   The most toxic of these chemicals is diazinon, with a Bilko Dose of 2.3´ 10-2 grams per year, and the least toxic is DEET, with a Bilko Dose of 2.3´101 grams per year.   The Risk Assessment Values used to calculate Bilko Doses for this set of 36 chemicals along with the toxicity parameter values used to calculate them are given in Table 3.


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Overview of the Bilko Index calculation:

Once the toxic chemicals found in the pesticides and cleansers used in a home have been identified and quantified, they can be combined with each product’s Usage Factor and each chemical’s Bilko Dose to find the home’s Bilko Index.   In broad overview, each toxic chemical’s contribution to the Bilko Index for a home is obtained by multiplying the mass in grams of each toxic chemical used in each product each year in and around the home by the product’s Usage Factor, and then dividing this value by the chemical’s Bilko Dose.   The contributions to the Bilko Index for all the chemicals used are added together to arrive at the home’s Bilko Index.

Each toxic chemical used in a home contributes to the home’s Bilko Index.   The contribution from each individual chemical to the Bilko Index is called its Bilko Indicator.   The Bilko Indicator is the sum of how much chemical is used in the home, adjusted by type of use for all the products containing the chemical, divided by the chemical’s Bilko Dose. In equation form, chemical i’s Bilko Indicator is

where Concentrationi,j is the concentration of chemical i in product j, Massj is the mass of product j used in the home each year, Usage Factorj is the Usage Factor of product j, Place Factorj is the Place Factor of product j, and Bilko Dosei is the Bilko Dose for chemical i.   The amount of product used and the Bilko Dose are both give in units of grams per year, so the Bilko Indicator is unitless.   The contributions for all the chemicals used in and around a home are added together to arrive at a home’s Bilko Index, or

Therefore, if only one of the toxic chemicals listed on the website is used in and around the home, then that chemical’s Bilko Indicator becomes the home’s Bilko Index.

An expanded formula for the Bilko Index is given here.

The following section discusses some of the objectives and constraints of the formula for calculating the Bilko Index.

 



Objectives and constraints of the Bilko Index equation:

One way to achieve the objective of educating visitors to the website is to make the means of obtaining the Bilko Index transparent.   To do this, the calculations for the Bilko Index have been explained and the results are reproducible.   The calculations apply uniformly across pesticide and cleanser products, and background data needed for calculating the Bilko Index, such as chemical properties, are available on the website.

Perhaps the greatest constraint on the calculation for the Bilko Index is that it require no more than a reasonable amount of information from visitors to the website.   This is important because the website needs to be an attractive rather than a burdensome place to visit.

Simpler means of calculating a home’s Bilko Index could be devised.   Perhaps the simplest means of establishing a toxicity rating would be to assign a score equal to the mass of the pesticides and cleansers used.   If this were the case, the Bilko Index for a home where one quarter of a pound per year of Grant’s Kills Ants â ant stakes and two pounds per year of Comet Disinfectant Cleanser â were used would have a Bilko Index of two and a quarter pounds.

However, while simple, this approach would be inadequate, in part because the chemicals contained in these products have very different toxicity levels.   Also, the concentrations of the toxic chemicals in these two products are not the same.   In addition, most of the Comet Disinfectant Cleanser â used is rinsed down the drain while the ant bait is left in place indefinitely.   Finally, the cleanser is usually applied indoors, while the ant bait is usually applied outdoors.  Therefore, adding the mass of the products used in order to obtain a toxicity rating value could be very misleading and result in misdirected efforts at reduction.

It would also be possible to use a more complicated means of calculating a home’s Bilko Index.   At this end of the spectrum would be a complex formula for calculating the Bilko Index that would take degree of toxicity into account as well as the conditions under which the chemical was used in order to get a more detailed picture of the amount of exposure and type of exposure to each chemical.   Factors including the use of gloves, the amount if any of the chemical that was spilled on the skin, the age and health status of individuals living in the home, and the ambient temperature at the time of application would need to be known.   The subsequent fate of the chemical would also need to be assessed.   Even chemicals that are intended to remain in place degrade over time or transport out of the immediate area, depending on weather and soil conditions.   However, taking these factors into account would require a great deal of time and effort on the part of visitors to the website without adding substantially to the usefulness of the Bilko Index as a means of guiding toxic reduction efforts.

The chosen approach for calculating the Bilko Index falls between these two extremes of complexity, so that the Bilko Index depends on quantities of toxic chemicals used, their degree of toxicity, and their mode of application, and whether they are used inside or outside.

In retaining a degree of simplicity, there are factors that can affect a chemical’s potential to cause toxic effects that are overlooked in the calculation of a home’s Bilko Index.   These factors include:

·        The age and socioeconomic and health status of people living in the home
Elderly people, children, and people with health problems are more likely to be affected by exposure to toxic chemicals, as are people whose access to health care is limited for social or economic reasons.   Based on the OP pesticide studies, children are exposed to an average of roughly four times as much residential toxic chemicals as adults living in a home, because of their stature and their patterns of activity.

 

·        The chemical’s fate in the environment once it is released
This is important in determining its potential for causing adverse effects. Some chemicals readily transfer from one environmental compartment (such as soil) to another (such as air), and some chemicals may quickly transform into other either more harmful or less harmful chemicals upon release.

 

·        Whether or not protective equipment and measures are used during application of the chemical
Protective equipment such as gloves and respirators can reduce the potential for a chemical to cause harm.   Based on the OP pesticide studies, applicators not wearing protective equipment are exposed to an average of roughly ten times as much toxic chemicals as other adults living in the home. Additionally, misuse of a chemical can increase the likelihood of an adverse effect.

Again, while the equation for calculating the Bilko Index neglects these factors, it is important to remember that the objective of the Bilko Index is not to quantify the risk for each individual from the use of pesticides and cleansers in the home.   Instead, the Bilko Index is meant to reflect the potential for these products use to cause adverse health effects in order to guide product choices. The equation, while pragmatic, provides for a far more meaningful value than a simple sum of the mass of toxic chemicals used.

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References

United States Department of Health and Human Services, National Toxicology Program, Chemical Repository, http://157.98.6.102/cgi/iH_Indexes/Chem_H&S/iH_Chem_H&S_Frames.html.

United States Department of Labor, Occupational Safety and Health Administration, Chemical Sampling Information, http://www.osha-slc.gov/dts/chemicalsampling/toc/toc_chemsamp.html.

United States Environmental Protection Agency (US EPA), “Risk-Screening Environmental Indicators, Version 1.0,” Office of Pollution Prevention and Toxics, http://www.epa.gov/opptintr/env_ind/index.html, July 1999.

United States Environmental Protection Agency (US EPA), “Pesticides Industry Sales and Usage, 1996 and 1997, Market Estimates,” 733-R-99-001, November 1999.

University of Tennessee’s Center for Clean Products and Clean Technologies, “Revised CHEMS Hazard Values,” March 8, 2001.

WestP2Net, “Janitorial Products Pollution Prevention Project, Ingredients to Avoid,” http://www.westp2net.org/Janitorial/tools/haz1.htm, not dated, a.

WestP2Net, “Janitorial Products Pollution Prevention Project, Ingredients to Avoid if Possible Or Use with Extreme Care,” http://www.westp2net.org/Janitorial/tools/haz2.htm, not dated, b.