U.S. patent application number 10/626006 was filed with the patent office on 2005-01-27 for nucleic acid based filters.
Invention is credited to Lyles, Mark B..
Application Number | 20050016555 10/626006 |
Document ID | / |
Family ID | 34080316 |
Filed Date | 2005-01-27 |
United States Patent
Application |
20050016555 |
Kind Code |
A1 |
Lyles, Mark B. |
January 27, 2005 |
Nucleic acid based filters
Abstract
The present invention provides a filter for removing carcinogens
from a gas or liquid. The filter contains nucleic acids, for
example DNA or apurinic acid, with which the carcinogens may react.
In specific embodiments the filters are used for tobacco smoke or
industrial pollutants.
Inventors: |
Lyles, Mark B.; (Great
Lakes, IL) |
Correspondence
Address: |
BAKER BOTTS L.L.P.
PATENT DEPARTMENT
98 SAN JACINTO BLVD., SUITE 1500
AUSTIN
TX
78701-4039
US
|
Family ID: |
34080316 |
Appl. No.: |
10/626006 |
Filed: |
July 24, 2003 |
Current U.S.
Class: |
131/332 ;
131/331 |
Current CPC
Class: |
A24D 3/14 20130101 |
Class at
Publication: |
131/332 ;
131/331 |
International
Class: |
A24D 003/06 |
Claims
What is claimed is:
1. A filter for a carcinogen reduction, the filter comprising: a
filtering surface operable to filter carcinogen-containing
material; and a carcinogen-reducing amount of nucleic acid.
2. The filter of claim 1, wherein the nucleic acid is distributed
on the filtering surface.
3. The filter of claim 2, wherein the nucleic acid is substantially
uniformly distributed on the filtering surface.
4. The filter of claim 1, wherein the nucleic acid provides
structural support to the filter.
5. The filter of claim 1, wherein the filter comprises at least
approximately 80% nucleic acid by weight.
6. The filter of claim 1, wherein the nucleic acid comprises
purified DNA.
7. The filter of claim 1, wherein the nucleic acid comprises
apurinic acid.
8. The filter of claim 1, wherein the carcinogen-containing
material comprises a polyaromatic hydrocarbon.
9. The filter of claim 1, wherein the carcinogen-containing
material comprises at least two carcinogens capable of reacting
with nucleic acid.
10. A filter for carcinogen reduction in tobacco smoke, the filter
comprising: a filtering surface operable to filter
carcinogen-containing tobacco smoke; and a carcinogen-reducing
amount of nucleic acid.
11. The filter of claim 10, wherein the nucleic acid is distributed
on the filtering surface.
12. The filter of claim 11, wherein the nucleic acid is
substantially uniformly distributed on the filtering surface.
13. The filter of claim 10, wherein the nucleic acid provides
structural support to the filter.
14. The filter of claim 10, wherein the filter comprises at least
approximately 80% nucleic acid by weight.
15. The filter of claim 10, wherein the nucleic acid comprises
purified DNA.
16. The filter of claim 10, wherein the nucleic acid comprises
apurinic acid.
17. The filter of claim 10, wherein the tobacco smoke comprises a
polyaromatic hydrocarbon.
18. The filter of claim 10, wherein the tobacco smoke comprises at
least two carcinogens capable of reacting with nucleic acid.
19. The filter of claim 10, wherein the filter is of a size and
shape that permits use as a cigarette filter.
20. The filter of claim 10, wherein the filter is of a size and
shape that permits use as an air-intake filter for an air
circulation system.
21. The filter of claim 10, wherein the filter is of a size and
shape that permits use in a portable air filtration system.
22. A filter for carcinogen reduction in combustion exhaust, the
filter comprising: a filtering surface operable to filter
carcinogen-containing combustion exhaust; and a carcinogen-reducing
amount of nucleic acid.
23. The filter of claim 22, wherein the nucleic acid is distributed
on the filtering surface.
24. The filter of claim 23, wherein the nucleic acid is
substantially uniformly distributed on the filtering surface.
25. The filter of claim 22, wherein the nucleic acid provides
structural support to the filter.
26. The filter of claim 22, wherein the filter comprises at least
approximately 80% nucleic acid by weight.
27. The filter of claim 22, wherein the nucleic acid comprises
purified DNA.
28. The filter of claim 22, wherein the nucleic acid comprises
apurinic acid.
29. The filter of claim 22, wherein the combustion exhaust
comprises a polyaromatic hydrocarbon.
30. The filter of claim 22, wherein the combustion exhaust
comprises at least two carcinogens capable of reacting with nucleic
acid.
31. The filter of claim 22, wherein the combustion exhaust
comprises exhaust from an internal combustion engine and wherein
the filter is of a size and shape that permits use in an internal
combustion exhaust system.
32. The filter of claim 22, wherein the filter is of a size and
shape that permits use in an industrial smoke stack.
33. A filter for carcinogen reduction in liquid effluent, the
filter comprising: a filtering surface operable to filter
carcinogen-containing liquid effluent; and a carcinogen-reducing
amount of nucleic acid.
34. The filter of claim 33, wherein the nucleic acid is distributed
on the filtering surface.
35. The filter of claim 34, wherein the nucleic acid is
substantially uniformly distributed on the filtering surface.
36. The filter of claim 33, wherein the nucleic acid provides
structural support to the filter.
37. The filter of claim 33, wherein the filter comprises at least
approximately 80% nucleic acid by weight.
38. The filter of claim 33, wherein the nucleic acid comprises
purified DNA.
39. The filter of claim 33, wherein the nucleic acid comprises
apurinic acid.
40. The filter of claim 33, wherein the combustion liquid effluent
comprises at least one carcinogen capable of reacting with nucleic
acid.
41. The filter of claim 33, wherein the combustion exhaust
comprises at least two carcinogens capable of reacting with nucleic
acid.
42. The filter of claim 33, wherein the filter is of a size and
shape that permits use in a liquid effluent outlet pipe.
43. A method for reducing the amount of carcinogen in a
carcinogen-containing material comprising passing the material
through a filter including: a filtering surface operable to filter
the carcinogen-containing material; and a carcinogen-reducing
amount of nucleic acid.
44. The method of claim 43, wherein the nucleic acid comprises
DNA.
45. The method of claim 43, wherein the nucleic acid comprises
apurinic acid.
46. The method of claim 43, wherein the carcinogen-containing
material comprises tobacco smoke.
47. The method of claim 43, wherein the carcinogen-containing
material comprises combustion exhaust.
48. The method of claim 43, wherein the carcinogen-containing
material comprises liquid effluent.
49. A method of making a filter for carcinogen reduction
comprising: forming a filtering material into a porous filter body;
applying to the filtering material a nucleic acid.
50. The method of claim 49, wherein the nucleic acid comprises
purified DNA.
51. The method of claim 49, wherein the nucleic acid comprises
apurinic acid.
52. The method of claim 49, further comprising: applying to the
filtering material a liquid solution comprising nucleic acid;
drying the filtering material.
53. The method of claim 52, further comprising applying a
crosslinking agent operable to covalently bond the nucleic acid to
the filtering material.
54. A method of making a filter for carcinogen reduction
comprising: purifying nucleic acid; and forming the purified
nucleic acid into a porous filter body.
55. The method of claim 54, wherein forming comprises adding an
aqueous nucleic acid solution to an alcohol solution in order to
precipitate nucleic acid into a porous filter body.
56. The method of claim 54, wherein the nucleic acid comprises
purified DNA.
57. The method of claim 54, wherein the nucleic acid comprises
apurinic acid.
Description
TECHNICAL FIELD
[0001] This invention relates to the field of filters. More
specifically, it is related to carcinogen-reducing filters formed
from nucleic acids and more specifically filters for cigarette
smoke.
BACKGROUND
[0002] Filters are generally used to remove an unwanted substance
from a desirable substance. This may be accomplished by a variety
of mechanisms, the two most prominent being size exclusion and
adherence to the filter. Because most carcinogens are small
molecules, adherence is the preferred method of carcinogen removal
by a filter.
[0003] Previously a wide variety of filters have been constructed
to remove carcinogens from other substances by inducing adherence
of the carcinogens to the filter. However, these filters are often
expensive, ineffective or dangerous or toxic themselves, among
other problems. Applications for such filters abound and range from
treatment of industrial effluents to removal or carcinogens, such
as polyaromatic hydrocarbons, from tobacco smoke. Accordingly, a
need exists for additional carcinogen-binding filters.
SUMMARY OF THE INVENTION
[0004] The present invention includes a filter for carcinogen
reduction. The filter may include a filtering surface operable to
filter carcinogen-containing material and a carcinogen-reducing
amount of nucleic acid.
[0005] In specific embodiments, the nucleic acid is distributed on
the filtering surface. More specifically, the nucleic acid may be
substantially uniformly distributed.
[0006] In other specific embodiments, the nucleic acid may provide
structural support to the filter. In some filters the nucleic acid
may comprise at least 80% of the filter by weight. In other
filters, the nucleic acid may comprise 85%, 90%, 95% or even 99% of
the filter by weight.
[0007] In specific embodiments, the nucleic acid comprises purified
DNA or apurinic acid. More specifically, the nucleic acid may
comprise 50%, 60%, 70%, 80% 90% or 95% DNA or apurinic acid,
respectively by weight, volume or mol/total mol nucleic acid.
[0008] In certain embodiments the carcinogen-containing material
may include a polyaromatic hydrocarbon. It may also include at
least two carcinogens capable of reacting with nucleic acid.
[0009] In one specific embodiment, the filter is operable to filter
carcinogen-containing tobacco smoke. In more specific embodiments,
the filter may be of a shape and size to permit use as a cigarette
filter, an air-intake filter for an air circulation system or a
filter in a portable air filtration system.
[0010] In another specific embodiment, the filter is operable to
filter carcinogen-containing combustion exhaust. In a more specific
embodiment the exhaust is from an internal combustion engine and
the filter is of a size and shape that permits use in an internal
combustion exhaust system. In another more specific embodiment, the
filter is of a size and shape that permits use in an industrial
smoke stack.
[0011] In yet another specific embodiment, the filter is operable
to filter carcinogen-containing liquid effluent and may be of a
size and shape that permits use in a liquid effluent outlet
pipe.
[0012] The invention also includes a method for reducing the amount
of carcinogen in a carcinogen-containing material by passing the
material through a filter of the present invention. In specific
embodiments the carcinogen-containing material may include tobacco
smoke, combustion exhaust and liquid effluent.
[0013] The invention includes a method of making a filter for
carcinogen reduction by forming a filtering material into a porous
filter body and applying a nucleic acid to the filtering material.
In specific embodiments, the nucleic acid includes purified DNA or
apurinic acid. In other specific embodiments, the nucleic acid may
be applied in a liquid solution. The filter material may then be
dried. After drying, a crosslinking agent may be applied to
covalently bond the nucleic acid to the filtering material.
[0014] The invention additionally includes a method of making a
filter for carcinogen reduction by purifying nucleic acid then
forming the purified nucleic acid into a porous body. This may be
accomplished, for example, by adding an aqueous nucleic acid
solution to an alcohol solution in order to precipitate nucleic
acid into a porous filter body. In specific embodiments, the
nucleic acid includes purified DNA or apurinic acid. In other
specific embodiments, the filter may also include other structural
materials bonded to the DNA, such as small silica particles.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] For a better understanding of the invention, reference may
be had to the following drawings and description of exemplary
embodiments.
[0016] FIG. 1 is a schematic drawing of a cigarette filter
according to an embodiment of the present invention.
[0017] FIG. 2 is a schematic drawing of an internal combustion
engine exhaust filter according to an embodiment of the present
invention.
[0018] FIG. 3 is a schematic drawing of a smoke stack filter
according to an embodiment of the present invention.
[0019] FIG. 4 is a schematic drawing of a liquid effluent filter
according to an embodiment of the present invention.
[0020] FIG. 5 is a schematic drawing of an air circulation system
filter according to an embodiment of the present invention.
[0021] FIG. 6 is a schematic drawing of a portable air filter
according to an embodiment of the present invention.
DETAILED DESCRIPTION
[0022] The present invention relates to a carcinogen filter
containing nucleic acids. In a specific embodiment, it relates to a
carcinogen filter containing DNA or apurinic acid. In some
embodiments the filter may be made primarily from another material
coated with nucleic acid or it may be formed from the nucleic acid.
Such filters may be used to remove carcinogens from any material
that may be passed through the filter. In specific embodiments they
may be used to remove polyaromatic hydrocarbons from air or tobacco
smoke.
[0023] Nucleic acids of the present invention may be any purified
nucleic acid. They may be naturally occurring or artificially
created. Nucleic acids specifically include apurinic acid, DNA (all
forms, including cDNA) and RNA (including mRNA, tRNA and rRNA) as
well as other nucleic acids.
[0024] The nucleic acid used in the present invention may be from
any source. Harvesting techniques for recovery of nucleic acid from
biological sources, including techniques capable of producing
commercial volumes of nucleic acids are readily known in the art.
Nucleic acids may be extracted from almost any biological source.
Two common sources of non-specific nucleic acid are fish sperm and
calf thymus. Almost any source, animal or plant-based, yeast or
bacterial may be used. These sources may be specifically developed
for nucleic acid harvest or may be waste products of other
commercial processes, as in the case of calf thymus. Because the
present invention employs nucleic acids for their chemical
properties alone, and not for their information coding properties,
the sequences of the nucleic acid may be irrelevant.
[0025] DNA, in certain examples, may be produced by solubilization
of cellular material with a detergent, followed by extraction of
nucleic acid from the aqueous layer with an alcohol. Various
additional steps and additives may assist in the removal of protein
to obtain purer nucleic acid. Various nucleases and extraction
techniques may be employed to destroy unwanted forms of nucleic
acids, such as RNA. Such techniques are well known in the art.
[0026] Nucleic acids may also be synthesized artificially from
nucleotides. For instance, surface catalysis techniques or
oligonucleotide synthesizers may be used.
[0027] The purity of nucleic acid from biological sources used in
compositions of the present invention may vary by application. In
most applications, the nucleic acid will contain no more than 50%
by weight residual matter from the biological source such as
proteins, lipids and carbohydrates. In certain embodiments, it will
contain no more than 25%, 10%, 5% or 1% by weight residual matter.
Such residual matter will likely include proteins, which may cause
unwanted effects such as bad taste in cigarette filters or
bacterial growth.
[0028] Nucleic acid is biodegradable and may also degrade due to
damage from carcinogens, many of which are known to cause breaks in
nucleic acid molecules. In many applications the rate of
degradation of nucleic acid will not be significant. However, the
rate may be influenced by the length of the nucleic acid molecule
used and type of nucleic acid as well as by treatment of the
nucleic acid.
[0029] The nucleic acid may also be crosslinked, although such
crosslinking may reduce the carcinogen removal properties of the
nucleic acid. Crosslinking may be between chains of a single DNA
molecule or between chains of two different nucleic acid molecules
or in any other possible permutation. Crosslinking may be
accomplished in a variety of ways, including hydrogen bonds, ionic
and covalent bonds, .pi..pi. bonds, van der Wals forces. More
specifically, crosslinking may be accomplished by UV radiation,
esterification, hydrolysis, or silica compounds, siloxane bridges
as described in U.S. Pat. No. 5,214,134, intercalating agents,
neoplastic agents, formaldehyde and formalin.
[0030] More than one type of crosslinking may be used in a given
composition. Furthermore, crosslinking may occur between two
strands of a nucleic acid molecule or between two separate nucleic
acid molecules.
[0031] Additionally, the nucleic acid may be methylated, ethylated,
alkylated, or otherwise modified along the backbone to influence
degradation rates. Generally, methylated, hemi-methylated,
ethylated, or alkylated nucleic acids will degrade more slowly.
Other backbone modifications affecting degradation rates include
the use of heteroatomic oligonucleoside carcinogen reduction
apacity of nucleic acid.
[0032] Nucleic acids may also be capped to prevent degradation.
Such caps are generally located at or near the termini of the
nucleic acid chains. Examples of capping procedures are included in
U.S. Pat. Nos. 5,245,022 and 5,567,810.
[0033] The size of the nucleic acid molecules used in filters of
the present invention may vary from as small as 2 bases to as long
as 10,000 bases or more. In general, most compositions will contain
nucleic acid molecules with a variety of lengths. In exemplary
embodiments, the average nucleic acid molecule length may be
between 50 and 500 bases.
[0034] Apurinic acid may be obtained using any known processes,
including the common process of hydrolysis of DNA in a strong acid
to remove purines. Apurinic acid may be created before or after
filter formation. It may also be treated in any suitable manner
such as those described above with respect to nucleic acids.
[0035] The nucleic acid and the filtering material of the present
invention may be provided as substantially pure chemical compounds
free from contaminants or in less pure forms. If contaminants are
present, it is preferred, especially in cigarette filters that the
contaminants are not themselves hazardous or do not decompose to
form hazardous compounds as the smoke passes through the
filter.
[0036] Selection of the filtering material in different embodiments
of the invention is pendent upon the end use of the filter. Likely
candidates for the filtering material are paper, cotton, cellulose,
cellulose acetate and glass fiber, with mixtures being possible.
When the filter is used as a tobacco smoke filter, the filtering
material conveniently is or includes cellulose acetate, the
currently most common cigarette filter material.
[0037] Filters of the present invention may be formed by a variety
of methods. In one method, an existing filter, such as a cellulosic
cigarette filter, is coated with nucleic acid. Coating may be
achieved in any suitable manner, including deposition from solution
and spray or aerosol deposition. In another method, nucleic acid
may be deposited on the filter material before the filter is
formed. In yet another method, the filter itself may use the
nucleic acid as a structural element and may even be made primarily
of nucleic acid.
[0038] In certain embodiments, the amount of nucleic acid that is
used varies depending upon the size of the filter. It appears
likely that nucleic acids remove carcinogens from materials by
forming complexes with the carcinogens. Although it is also
possible that nucleic acids may remove carcinogens by other
methods, such as chemically altering the carcinogens, for selected
embodiments of the present invention, it is assumed that complexes
are formed. Accordingly, in such embodiments, it is assumed that
the life of a filter will be relatively longer with an increased
amount of nucleic acid present. Therefore, the amount of the
nucleic acid used in the filter can be selected so as to
substantially cover the surface of the filtering material In more
specific embodiments the amount of nucleic acid used in the filter
covers at least about 5% of the surface of the filtering material.
It may also cover at least about 10%, 15%, 20%, 30%, 40%, 50% or
higher. In even more specific embodiments, the nucleic acid is
substantially uniformly distributed on the surface of the filtering
material. In other embodiments, the filter may be substantially
formed from nucleic acid. More specifically, the filter may include
at least 50%, 60%, 70%, 80%, 90%, 95% or even 99% nucleic acid by
weight or filter material volume.
[0039] In one aspect of this embodiment, the filter is a cigarette
filter including the filtering material and a nucleic acid free
from hazardous contamination or any masking agent that may
interfere with carcinogen removal. The nucleic acid is distributed
on the surface of the filtering material. The amount of nucleic
acid present is sufficient to substantially eliminate carcinogens
capable of reacting with the nucleic acid from the tobacco smoke
that passes through the filter. In a more specific embodiment, the
nucleic acid is used in an amount that does not adversely affect
the cigarette taste.
[0040] In another embodiment of the present invention, the filter
is actually formed from nucleic acid as a structural material. The
nucleic acid may be the primary structural material or may be
combined with substantial amounts of other filter material.
[0041] Filters of the present invention may remove any carcinogen
capable of reacting with the nucleic acid in the filter. Filters
may differ in their efficiency of removal of different carcinogens.
In selected embodiments, filter may be specifically tailored for
removal of certain carcinogens, such as polyaromatic hydrocarbons
from tobacco smoke, even if this results in less efficient removal
of other carcinogens.
[0042] Filters of the present invention may be used to remove
carcinogens from any source. The chemical makeup of the filter and
the physical construction and shape may be adapted to facilitate
removal of specific carcinogens or to accommodate a particular
source. In specific examples the source is a gas or liquid. In more
specific embodiments, the liquid may contain carcinogens in
solution or in suspension.
[0043] In specific embodiments, the filters may be designed for
removal of smoke from air. "Smoke" generally means the gaseous
product of burning a carbonaceous material, usually made visible by
the presence of small particles of carbon. Smoke containing
carcinogens results, for example, from the pyrolysis of tobacco and
the combustion of fuel by an internal combustion engine,
particularly a diesel engine. Industrially, certain pyrolysis
process smokes contain carcinogens.
[0044] In certain embodiments, DNA may serve as a good filter or
filter coating for removal of polyaromatic hydrocarbons from
tobacco smoke. In this embodiment of the filter of the present
invention, the filter may be of a size and shape that permits use
as a tobacco smoke filter. As a tobacco smoke filter, the filter is
particularly useful as a cigarette filter, a filter in a cigarette
or cigar holder, or a filter for a pipe.
[0045] In one embodiment of the present invention, shown in FIG. 1,
the filter is primarily for the filtration of tobacco smoke. In
this embodiment, a filter 10 having a filtering material 12 is
illustrated in use on a cigarette 14. The filter may have a conical
cavity (not shown) or may have the configuration of a convention
filter as depicted. The filter may be any type of filter of the
present invention. In a more specific embodiment, it is a
cellulosic filter coated with DNA or apurinic acid.
[0046] In a more specific embodiment, the filter contains a
filtering material having a filtration surface area and airflow
characteristics that in the normal untreated (no nucleic acid)
state will provide removal of at least about 40-45% of the total
particulate matter from the smoke passing through it. In an even
more specific embodiment, the filtering material may have a
filtration surface area and airflow characteristics that provide
removal of at least about 50% of the total particulate matter from
the smoke, or as much as 60-95% removal may be achieved in some
embodiments.
[0047] In other specific embodiments, the nucleic acid may be
substantially uniformly distributed on the surface of the filtering
material. However, in other specific embodiments, where the airflow
characteristics of the filter are such as to provide for
ventilation of fresh air into the filter as a result of which the
effective filtration surface area is reduced because of channeling
of the smoke to certain areas of the filter, the nucleic acid may
be substantially uniformly distributed over the effective
filtration surface area of the filtering material.
[0048] Presently, in the manufacture of some commercial cigarette
filters in the United States, ventilation of fresh diluting air
into the filters is provided. As a result of fresh air ventilation,
smoke is channeled through only a portion of the available
filtration surface area. Thus, the effective filtration area in
filters of this type is less than the available filtration surface
area. Accordingly, the airflow characteristics of a filter may
include fresh air ventilation. Other ways to affect the available
filtration surface area by varying airflow characteristics are
known in the filter making art. In general, filters of the present
invention have recommended amounts of nucleic acid on surfaces over
which smoke flows. The inclusion of nucleic acids on surfaces over
which only fresh air or relatively smoke-free air flows is not as
critical in certain embodiments of the present invention.
[0049] In a conventional fibrous tobacco smoke filter, the
efficiency of the filter is related to the surface area of the
fibers and the linear velocity of the smoke. For example, a typical
fibrous filter with a surface area of 275 cm.sup.2 has a pressure
drop of about 2.8 inches and a filtration efficiency of about 46%.
When the surface area of this conventional filter is increased
substantially by adding more fibers, the pressure drop of the
filter is increased beyond the practical limit. For example, if the
surface area of this filter is increased to about 500 cm.sup.2 by
adding more fibers, the efficiency of the filter is increased to
about 66%, but the pressure drop is increased to about 7.5 inches.
The filtration coefficient may be calculated from this data by the
following equation:
k=[-Ln(1-R)].DELTA.P,
[0050] where R represents the filtration efficiency or percent of
total particulate matter removed, and .DELTA.p is the pressure
differential across the filter. The value of k for conventional
filters made from textile tows is between 0.13 and 0.22 depending
on the size and type of fibers (assuming .DELTA.p is expressed in
inches of water at an airflow rate of 17.5 ml/sec.).
[0051] A conventional filter, having substantially uniform density
from one end of the filter to the other, customarily used
commercially in the United States has a filtration surface area and
airflow characteristics that provide removal of about 40-45% of the
total particulate matter from tobacco smoke. This type of filter
generally has a total denier of at least 30,000, with an increase
in surface area being provided by use of a relatively lower
individual fiber denier, for a constant total denier. The filtering
materials of the Marlboro.RTM.and Winston.RTM. filters are each
believed to have a filtration surface area and airflow
characteristics that provide removal of about 40-45% of the total
particulate matter from tobacco smoke. In this regard, the Marlboro
filter is believed to be characterized by about 36,000-42,000 total
denier provided by individual fibers of about 3.6-4.2 denier, and
characterized by about 5-15% fresh air ventilation.
[0052] Another type of filter used commercially in the U.S. is
characterized by nonuniform density from one end of the filter to
the other. One example of this type of filter has a
conically-shaped cavity. Filters of this type are illustrated by
U.S. Pat. No. 4,064,791 to Berger, the filter of which removes 60%
or more of the total particulate matter. Other filters having a
filtration surface area and airflow characteristics that provide
removal of at least about 60%, and even up to about 95% of the
total particulate matter from tobacco smoke are illustrated by U.S.
Pat. Nos. 3,648,711, 3,599,646, and 3,533,416. The filtering
material of the Vantage.RTM. filter is believed to have a
filtration surface area and airflow characteristics that provide
removal of at least about 60% of the total particulate matter.
[0053] For purposes of the description contained herein, the
percent of total particulate matter removed by the filtering
material of the present invention is to be understood to exist when
the pressure drop across the filter is about 2.0 to 2.5 inches of
water, with up to 3 inches of water being contemplated. A pressure
drop greater than about 3.0 is objectionable and not acceptable to
the majority of cigarette smokers.
[0054] In a specific illustration of the embodiment of the present
invention in which the filter is of a size and shape that permits
use as a cigarette filter, the nucleic acid is DNA. The size of
this cigarette filter is about 19 to 25 mm in length and about 7.8
mm in diameter. The amount of DNA in this filter is that amount
provided by applying about 0.3 ml of an aqueous saturated DNA
solution onto the filtering material of the cigarette filter. The
aqueous solution is preferably applied by injection into the
approximate midpoint of the filter. The amount of DNA distributed
on the filtering material is about 5-7 mg.
[0055] In another embodiment of the present invention shown in
FIGS. 2 and 3, a filter 30 is used in conjunction with an exhaust
system of an internal combustion engine or in conjunction with an
industrial smoke stack. The filter comprises a filtering material,
32 with DNA or apurinic acid distributed on its surface. When the
filter is used on an industrial smoke stack, a fan or ejector may
be employed in order to provide an adequate smoke flow through the
smoke stack. In FIG. 2, filter 30 is shown in use on stack 34, and
fan 36 is also shown. In FIG. 3, filter 30 is shown as part of an
exhaust system 38 of an internal combustion engine 40. One suitable
location of filter 30 in exhaust system 38 is shown in this figure.
A location of the filter on the other side of muffler 42 is also
possible.
[0056] In yet another embodiment of the present invention shown in
FIG. 4, a filter 50 is used in conjunction with a liquid effluent
system. This liquid effluent system may be used in connection with
an industrial process, such as paper processing, or as wastewater
treatment, for example of water used to clean cement in gas station
filling areas. Other processes in which carcinogens are introduced
into a liquid effluent may also be used with the system of FIG. 4.
In the embodiment depicted, the filter 50 is located in an effluent
outlet pipe 52, which carries effluent 54 from a source 56 to a
dump area 58. Additional treatment equipment 60 may also be
connected to outlet pipe 52 for additional treatment of effluent
54, although such equipment is not required in all embodiments.
[0057] In the embodiment of the invention depicted in FIG. 5, a
filter 70 is part of an air circulation system. In the embodiment
depicted, filter 70 is located near an air intake 72 and removed
carcinogens before air reaches circulator 74. This embodiment may
have the advantage of avoiding carcinogen build-up in circulator
74. However, in other embodiments the filter may be located at any
point prior to air outlet 76. The embodiment of FIG. 5 shows use of
filter 70 in a home air circulation system. A similar system may be
adapted for commercial settings. Although only one air intake is
depicted in FIG. 5, filters of the present invention are compatible
with multiple intake systems. In multiple intake systems all
filters in air intakes may be filters of the present invention, or
filters of the present invention may be limited to air intakes in
areas where carcinogens are likely to be introduced into the air,
such as smoking areas or laboratory areas designed for airborne
carcinogen use.
[0058] In the embodiment depicted in FIG. 6, filter 80 is part of a
portable air filtration system. Such system may be designed and
used for home or commercial use. In specific embodiments, it is
designed to regularly remove carcinogens from a small area. In
other embodiments, it may be designed for emergency use, such as
removal of carcinogens from a locality after a chemical spill or
during warfare.
[0059] In the embodiments depicted in FIGS. 5 and 6, the filter may
be prepared, in more specific embodiments, by coating a
commercially available air filter otherwise suited for the
appurtenant equipment with DNA or apurinic acid. Such coating may
be achieved as described above in relation to cigarette filters. It
is preferred that the coating not substantially reduce air flow
through the filter and that the coating be in amount sufficient to
substantially remove carcinogens from air passing through the
filter when used as intended for the recommended filter life. For
example, a filter designed to last for two months in a home smoking
environment may be coated with a sufficient amount of nucleic acid
to substantially remove the amount of carcinogens capable of
removal by nucleic acids and expected to be in the air of a
stay-at-home smoker who smokes the national average number of
cigarettes a day for at least two months.
[0060] All of the compositions and/or methods disclosed and claimed
herein can be made and executed without undue experimentation in
light of the present disclosure. While the filters and methods of
this invention have been described in terms of specific
embodiments, it will be apparent to those of skill in the art that
variations may be applied to the filters and/or methods and in the
steps or in the sequence of steps of the methods described herein
without departing from the concept, spirit and scope of the
invention. All such similar substitutes and modifications apparent
to those skilled in the art are deemed to be within the spirit,
scope and concept of the invention.
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