United States EPA-600/R-01-001

Environmental Protection

Agency January 2001

Research and

Development

CANDLES AND INCENSE AS

POTENTIAL SOURCES OF

INDOOR AIR POLLUTION:

MARKET ANALYSIS AND

LITERATURE REVIEW

Prepared for

Office of Research and Development

Prepared by

National Risk Management

Research Laboratory

Research Triangle Park, NC 27711
FOREWORD

The U. S. Environmental Protection Agency is charged by Congress with protecting the Nation's land, air, and water resources. Under a mandate of national

environmental laws, the Agency strives to formulate and implement actions leading to a compatible balance between human activities and the ability of natural

systems to support and nurture life. To meet this mandate, EPA's research

program is providing data and technical support for solving environmental problems today and building a science knowledge base necessary to manage our ecological resources wisely, understand how pollutants affect our health, and prevent or reduce environmental risks in the future.

The National Risk Management Research Laboratory is the Agency's center for

investigation of technological and management approaches for reducing risks

from threats to human health and the environment. The focus of the Laboratory's

research program is on methods for the prevention and control of pollution to air,

land, water, and subsurface resources, protection of water quality in public water

systems; remediation of contaminated sites and-groundwater; and prevention and

control of indoor air pollution. The goal of this research effort is to catalyze

development and implementation of innovative, cost-effective environmental

technologies; develop scientific and engineering information needed by EPA to

support regulatory and policy decisions; and provide technical support and information transfer to ensure effective implementation of environmental regulations

and strategies.

This publication has been produced as part of the Laboratory's strategic longterm research plan. It is published and made available by EPA's Office of Research and Development to assist the user community and to link researchers

with their clients.

E. Timothy Oppelt, Director

National Risk Management Research Laboratory

EPA REVIEW NOTICE

This report has been peer and administratively reviewed by the U.S. Environmental

Protection Agency, and approved for publication. Mention of trade names or

commercial products does not constitute endorsement or recommendation for use.

This document is available to the public through the National Technical Information

Service, Springfield, Virginia 22161.
E PA-600/ R-01-001

January 2001

CANDLES AND INCENSE AS POTENTIAL 

SOURCES OF INDOOR AIR POLLUTION:

MARKET ANALYSIS AND 

LITERATURE REVIEW

PREPARED BY:

Lynn Knight, Arlene Levin, and Catherine Mendenhall

Eastern Research Group, Inc.

110 Hartwell Avenue

Lexington, MA 02421

EPA Contract 68-D7-0001

EPA Project Officer: Zhishi Guo

National Risk Management Research Laboratory

Research Triangle Park, NC 27711

PREPARED FOR:

U.S. Environmental Protection Agency

Office of Research and Development

Washington, D.C. 20460
ii

Abstract

The report summarizes available information on candles and incense as potential sources of

indoor air pollution. It covers (1) market information and (2) a scientific literature review. The

market information collected focuses on production and sales data, typical uses in the US, and

data on the sources and quantities of imported products. The estimated total sales of candles in

1999 varied between $968 million and $2.3 billion, while imports were $486 million. The US

imports and exports of incense in 1999 were $12.4 and 4.6 million, respectively. The scientific

literature review gathered information regarding the emission of various contaminants generated

when burning candles and incense, as well as the potential health effects associated with 

exposure to these contaminants. Burning candles and incense can be sources of particulate

matter. Burning candles with lead core wicks may result in indoor air concentrations of lead

above EPA-recommended thresholds. Exposure to incense smoke has been linked with several

illnesses, and certain brands of incense also contain chemicals suspected of causing skin

irritation.
iii

Table of Contents

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii

Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

1. Findings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.A Economic Data on Candle and Incense Production and Sales . . . . . . . . . . . . . . . . . . 1

1.B Potential Indoor Air Quality Impacts of Burning Candles and Incense . . ......... 2

2. Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3. Economic Data on Candle and Incense Production and Sales . . . . . . . . . . . . . . . . . . . . . . . . . 5

3.A Candles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Number of Candle Manufacturers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Sales . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Market Trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Sources of Imported Candles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Product Use in the US . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

3.B Incense . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

4. Potential Indoor Air Quality Impacts of Burning Candles and Incense . . . . . . . . . . . . . . . . . 21

4.A Candles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Lead Wick Emissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Other Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Organics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
iv

Particulate Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Candle Soot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

4.B Incense . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Carbon Monoxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Isoprene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Benzene . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Musk Xylene, Musk Ketone, and Musk Ambrette . . . . . . . . . . . . . . . . . . . . . . . . 36

Particulate Matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Polyaromatic Hydrocarbons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

5. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
v

Tables

Table 1: Total Sales of Candle Companies in 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Table 2: Percent of Candle Sales by Distribution Channel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Table 3: 1999 Candle Imports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Table 4: Sources of Imported Candles in 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Table 5: 1999 Imports of Odoriferous Preparations Which Operate By Burning . . . . . . . . . . . . 19

Table 6: Indoor Air Impacts of Burning Candles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
1

1. Findings

The purpose of this report is to collect economic information regarding the production and sales

of candles and incense in the US, including information about imports. A second objective is to

review the scientific literature regarding emission rates and potential human health effects

associated with burning candles and incense. The following is a brief overview of the findings.

1.A ECONOMIC DATA ON CANDLE AND INCENSE PRODUCTION AND SALES

• The Census Bureau reports 107 manufacturing establishments; however, industry

estimates range from 160 to over 200 manufacturers. Many manufacturers are very small. 

• Candle sales have been growing rapidly in the last 10 years (10 to 15 percent per year),

fueled by consumer interest in aroma therapy and increased demand for home fragrance

products in general.

• The Census Bureau reports a total value of shipments in 1997 of $968 million; industry

estimates put 1999 sales at $1.3 billion just for scented candles, and up to $2.3 billion for

all candles.

• The top five countries that export candles to the US are China, Taiwan, England, Hong

Kong, and Mexico.
2

• There are no public data on incense manufacturers; private data show at least 26

manufacturers. Limited discussions with some industry representatives indicate that there

are probably many more very small manufacturers.

• The top five countries that export incense to the US are India, China, Thailand, Japan, 

and Hong Kong.

1.B POTENTIAL INDOOR AIR QUALITY IMPACTS OF BURNING CANDLES AND INCENSE

• Burning candles containing lead core wicks can result in indoor air concentrations of lead

above EPA-recommended thresholds.

• In the scientific literature we reviewed, zinc and tin were found not to be emitted at

concentrations that would raise concerns when burned indoors.

• One study showed worst-case scenario concentrations of acrolein, formaldehyde, and

acetaldehyde from candle emissions exceeding EPA-recommended thresholds. 

• Sooting can occur when combustion conditions are impaired when burning candles. 

Scented candles are more likely to produce soot than unscented candles. Sooting can
3

cause property damage by blackening surfaces. We could not identify any studies on

potential human health effects associated with soot from candles.

• Several studies indicated links between exposure to incense smoke and health effects,

including cancers and contact dermatitis. A few studies indicated possible mutagenic and

genotoxic effects.

• Studies that examined the emissions of specific contaminants from incense smoke

indicated that benzene and particulate matter may be emitted at concentrations that could

pose human health risks.
4

2. BACKGROUND

The potential indoor air impacts of burning candles and incense have drawn increased attention 

in recent years. For example, candles with lead wicks have been found on the market and have

been shown to emit lead when burned. Sooting associated with burning candles can cause

property damage by blackening walls, ceilings, and carpets. Incense smoke can be a major

source of particulates in indoor air. Emissions from incense may contain contaminants that can

cause a variety of health effects.

EPA is currently testing the emissions from candles and incense to generate data for analyzing

risk management options. To support this effort, this report collects and presents information on

the production and sales of candles and incense, the sources and quantities of imported products,

and the typical product uses in the US. This information will help EPA in assessing the nature

and extent of human exposure. In addition, this report summarizes the results and findings in the

scientific literature regarding the emission rates of the various contaminants generated when

burning candles and incense, as well as the potential health effects associated with exposure to

these contaminants. EPA will use this information to further their research and understanding of

the potential impacts of these sources on indoor air quality.
5

3. ECONOMIC DATA ON CANDLE AND INCENSE PRODUCTION AND 

 SALES

3.A CANDLES

A variety of candle types are manufactured in the US, including tapers, straight-sided dinner

candles, spirals, column, votives, tealights, wax-filled containers, and novelties. Some are

scented and all come in a wide range of colors. Wax candles contain petroleum wax, vegetable

wax, animal wax, or insect wax as the primary fuel. The wax may contain additives for color,

fragrance, stability, or to modify the burning characteristics.

Gel candles use liquids such as mineral oil, terpene-type chemicals, or modified hydrocarbons as

their primary fuel. These candles also contain chemical agents to increase the viscosity of the

fuel to the point where the candle has a quasi-rigid property.

Candles support one or more combustible wicks. Metal is put in some wick cores to keep the

wick standing straight when the surrounding wax begins to melt. The metal prevents the wick

from falling over and extinguishing itself as soon as the wax fails to support it. Many companies

use a braided wick, which consists of three smaller wicks wound together to provide some

stiffness.

Lead was commonly used as a core material until 1974 when the US candle manufacturing

industry voluntarily agreed to discontinue use of lead in wicks. There are, however, still candles
on the market that contain lead wick cores. Most of these are imported. Zinc is commonly used

as an alternative metal core for the wicks, since it provides the desired amount of stiffness, burns

off readily with the rest of the wick, and the airborne particles from zinc wicks are considered

safer.1

Scented candles have grown in popularity and are widely used. The majority of candle

manufacturers offer scented candles. Seventy-five percent of the manufacturers who are

members of the National Candle Association (NCA) listed fragranced candles among the types of

candles they produce. Forty percent say they manufacture citronella candles (NCA, 1999).

Citronella is an insect repellant.

Number of Candle Manufacturers

The candle industry is a relatively small industry and does not have an abundance of publicly

available data. The 1997 Economic Census published by the US Census Bureau reports 107

manufacturing establishments with a primary North American Industry Classification System

(NAICS) product classification code of 3399995, defined as “candles, including tapers” (US

Census Bureau, 1999). These establishments collectively employed 8,536 workers. The Census

Bureau has very limited data available since the industry is identified at the 7-digit level.

ERG conducted an online search of the Thomas Register of American Manufacturers. This

1

Telephone communication between Marianne McDermott, Executive Vice President, National Candle

Association, and Lynn Knight, ERG, August 18, 2000.

6
7

search identified 160 candle manufacturers. However, the National Candle Association (NCA)

estimates there are over 200 known commercial, religious, and institutional manufacturers of

candles in the US, as well as many small craft producers (NCA, 1999). The NCA reports that 70

of their members are manufacturers and represent roughly 80 percent of the market. The three

largest publicly traded manufacturers are Candle Corporation of America, Candle-Lite, Inc., and

The Yankee Candle Company, Inc. (NCA, 1999). A Merrill Lynch Global Securities analyst

reported that Yankee Candle Co. accounts for about 10 percent of industry sales. It has 100

stores and plans to open 40 per year (Fort Worth Star-Telegram, 1999).

A private market study by the Packaged Facts group reports that the candle industry is not only

growing, but is undergoing some consolidation. This trend is not limited to smaller companies,

but has included some of the leading manufacturers and marketers succumbing to stronger, better

financed companies (Packaged Facts, 1999). This source believes that company buyouts are

motivated by parent organizations attracted to making acquisitions in a thriving market and then

helping these acquisitions grow their product lines and increase market share. For example,

Yankee Candle’s partnership with Forstmann Little was reportedly undertaken specifically to

fund a major expansion (Packaged Facts, 1999).

Internet sales of candles have been increasing. Many smaller candle companies are emerging and

doing well selling their products on the Internet, as the appearance of prominence can be 

obtained with a nice looking Web site. Selling on the Internet allows these manufacturers to sell
8

candles at a reasonable price, since they can pass on savings accrued by avoiding middlemen,

slotting fees paid to retailers, and advertising costs (Packaged Facts, 1999).

There have been many types of new entrants to the growing candle market. Market research

analysts believe that new marketers are attracted to this burgeoning market because candles are

relatively simple to make, color, and fragrance, and novelty designs easily attract the buyer’s

attention (Packaged Facts, 1999). The scented candles market has seen a lot of cross-category

encroachment, as fashion designers, perfume manufacturers, and specialty chain marketers

introduce their own lines of candles. For example, upscale retailers, such as The Gap, Pottery

Barn, Pier One, and the Bombay Company, are marketing scented candles under their own

trademark. SC Johnson, too, began selling candles fragranced with many of Glade’s air freshener

trademark scents (Packaged Facts, 1999). Meanwhile, dedicated candle outlets, like Yankee

Candle, White Barn Candle Company, and Illuminations, are expanding throughout the US

(Packaged Facts, 1999).

Sales

The 1997 Economic Census reports a total value of shipments for candle manufacturers of 

$968.3 million. Companies with shipments of $100,000 or more accounted for 98 percent of

shipments, or $951 million. In 1992, shipments for these larger companies were $366 million. 

The value of shipments increased more than 2.5 times over this 5-year period.
The NCA states that the US candle consumer retail sales for 1999 are reported at $2.3 billion, not

including candle accessories. NCA further reports that sales of all candles (unscented, scented,

and for institutional and religious uses) have been growing 10 to15 percent a year since 19902

(NCA, 1999). The Packaged Facts report claims that the growth of scented candles alone is close

to 22 percent per year. This same report estimates that scented candles represent 55 percent of the

$2.4 billion total home fragrance market, or $1.3 billion in scented candle sales. Another source,

The Freedonia Group, estimated that 1999 candle sales were $1.17 billion.3

Unity Marketing, another private marketing research firm, conducts annual surveys among gift

manufacturers who produce and market candles and candle accessories. The most recent survey,

which had 37 respondents, was conducted in 2000 and covered 1999 sales. The survey results

showed an upward trend in total annual sales for 1999, with average company sales among

respondents up 39 percent from $10 million in 1997 to $14 million in 2000. In 1999, 39 percent

of companies surveyed reported annual sales of more than $10 million as compared with only 27

percent in 1997. (See Table 1.)

2

The source of these estimates is not disclosed in the NCA publication.

3

This figure was interpreted from the Freedonia Group’s prediction that sales would increase 8.1 percent 

annually to reach $1.6 billion in 2003.

9
10

Total Annual Sales

(Dollars in Thousands)

Percent of Candle

Companies Surveyeda

> $50,000 12

$26,000 - $50,000 9

$11,000 - $25,000 18

$6,000 - $10,000 9

$1,000 - $5,000 27

$500 - $999 15

<$500 12 a

These statistics do not cover only candle manufacturing. They include 

manufacturers of candle accessories as well. Fifty-three percent of 

companies surveyed owned their own factory facilities. Figures do not 

add to 100 percent.

Source: Unity Marketing, 2000.

Table 1: Total Sales of Candle Companies in 1999

Candles are sold through a variety of distribution channels. According to the Unity Marketing

survey, specialty retail stores capture a large portion of candle sales. (See Table 2.) Packaged

Facts estimates that 51 percent of 1998 scented candle sales were attributable to mass

merchandisers, 36 percent to supermarkets, and 13 percent to drug stores. (Unity Marketing and

Packaged Facts each based their estimates on different distribution channel categories, thus not

allowing direct comparisons.)
11

Distribution Channel Percent of Total

Specialty Retail Stores (gift, card, collectible,

and decorative accessory shops)

68

Department Stores 9

Mass Merchandisers and Discounters 8

Internet 4

Consumer Direct Marketing

(catalogs, direct response ads, or promotional

mailings)

4

Other 7

Source: Unity Marketing, 2000.

Table 2: Percent of Candle Sales by Distribution Channel

Market Trends

In their reporting of product statistics, the Economic Census reports nearly a doubling in the

number of candle manufacturers from 1992 to 1997. As discussed above, recent years have

shown new entrants to the candle manufacturing industry. Although many new manufacturers

have entered the market, according to a the Unity Marketing survey, the majority (75 percent) of

gift manufacturers that produce and market candles and candle accessories have been in the

business for a long time. Half of the companies in the survey have been in business for 11 to 25

years, while another 25 percent have been in business longer.

The NCA reports that, in the last 5 years, the industry has doubled its sales. Trade association

sources as well as numerous trade publication articles attribute this tremendous growth to the
12

rapid increase in sales of aroma therapy and other scented candles. A supermarket trade

publication reported that in 1999, candles were generating annual sales increases of around 20

percent (Supermarket News, 1999). The same publication states that retailers and suppliers

attribute the upswing in sales to the fact that consumers view candles as a relatively cheap and

accessible fashion accessory for the home for special events or seasonal decoration, or just as an

accessible means of augmenting the atmosphere within the home.

Shipments of candles are forecast by the Freedonia Group, a private research firm, to expand 8.1

percent per year reaching $1.6 billion in 2003 (The Freedonia Group, Inc., 1999). They predict

that, in addition to the mature market for ceremonial and utilitarian lighting applications,

introduction of numerous fashion-driven, upscale offerings and mood-enhancing scented

varieties, will spur gains; as will the increasing market presence of candle-only stores. 

Supermarkets, drug store chains, and upscale department stores have all expanded their candle

offerings, including displays in multiple departments, such as air-freshener, body/bath sections,

and health and beauty products displays.

The Freedonia Group report predicts that the pace of growth will slow from the double-digit

increases of the earlier decade, due to increased competition from imports and some loss of

consumer interest. This is in contrast to the Packaged Facts report that observes that, even 

though the trade press has previously reported that the popularity of candles and potpourri 

usually alternates on a 5-year cycle, candles are continuing to sell beyond that cycle and are
13

showing no signs of slowing down.

Another business publication reports that candles are the largest growing segment in the giftware

market. Sales have been buoyed by the introduction of high-fashion candle stands and display

accessories as well as innovations in candle design, shape, color, and fragrances. Longer lasting

scents and unique decorative styles have attracted buyers. Females between the ages of 25 and 54

with household annual incomes over $25,000 are the prime market. Men purchase candles at

about half the rate of women (Business Wire, 1999).

Sources of Imported Candles

The Census Bureau tallies import data from the various ports of entry by originating country. 

These data show that in 1999, China, Hong Kong, Mexico, and Canada were the largest suppliers

of candle imports. (See Table 3.) A total of 197.9 million kg of candles valued at $484.2 million

were imported in 1999. The Freedonia Group reports that candle imports more than tripled

between 1993 and 1998.

Unity Marketing investigated the sources of imports when surveying candle manufacturers. (See

Table 4.) This survey showed that 68 percent of companies reported China as the top country

supplying imported candles.
14

Country of Origin Quantity (kg) Percent of Total Custom Value

China 68,922,143 34.8 $131,759,756

Hong Kong 26,506,500 13.4 $53,548,145

Mexico 25,449,253 12.9 $50,868,810

Canada 24,781,312 12.5 $73,683,421

Guatemala 8,529,417 4.3 $55,737,602

Israel 8,395,482 4.2 $19,425,929

Thailand 7,532,504 3.8 $18,439,677

Taiwan 6,876,205 3.5 $17,525,569

Italy 4,722,934 2.4 $13,162,283

El Salvador 2,594,292 1.3 $3,332,61

Macao 2,227,634 1.1 $4,474,057 a

Table includes data only from countries supplying 1 percent or greater of the total quantity of imports.

Source: US Bureau of the Census, 2000.

Table 3: 1999 Candle Importsa
15

Country Percent of Companies

Surveyed

China 68

Taiwan 40

England 36

Hong Kong 36

Mexico 36

Philippines 25

Thailand 25

Indonesia 21

France 18

Italy 18

Malaysia 18

Germany 14

Japan 14

Spain 11

Australia & New Zealand 7

Ireland 7

Poland 7

India 7

Brazil 4

Canada 4

Singapore 4

Other 7

Source: Candle Report, Unity Marketing, 2000.

Table 4: Sources of Imported Candles in 1999

 
16

Product Use in the US

Candles are purchased for utilitarian, religious, or other institutional purposes, but the majority of

candles, particularly scented candles, are purchased for non-utilitarian home use. Consumers

buying scented candles derive utility from the decorative and aromatic attributes of the candles. 

The NCA reports that 7 out of 10 US households use candles, and candle manufacturers’ surveys

show that 96 percent of all candles purchased are bought by women (NCA, 1999).

Some candles are purchased for special events, such as parties, or for seasonal decorations. Thus

candle sales do especially well in parts of the country that experience four seasons. Impulse

buying accounts for a significant portion of purchases on a regular basis because people are

attracted to the scent when they encounter candles while shopping (Supermarket News, 1999).

People encounter candles more often as supermarkets, drug stores, and mass-merchandisers

increase their candle offerings. Candles are sold alongside floral and gift merchandise, as well as

greeting cards. Candles for home decorating and fragrance have broad appeal, crossing all

demographic lines (Supermarket News, 1999). The NCA reports that seasonal (e.g., Christmas

and other holidays) buying accounts for roughly 35 percent of sales (NCA, 1999).

3.B INCENSE

Incense has been used for centuries for ceremonial purposes as well as to fragrance the

environment, conceal undesired ambient odors, or freshen clothing. Most incense is made from a

combination of fragrant gums, resins, woods, and spices. One traditional method of making

incense is to prepare a paste of pulverized botanicals, water, and charcoal and wrap the paste
17

around a bamboo twig. After the twig dries, it is dipped into perfumed essential oils or powders.

Incense is available in sticks, cones, rods, coils, small blocks, wands, and powders (Packaged

Facts, 1999).

The US Census Bureau does not maintain data to the level of detail required to capture incense

manufacturers. Economic data for incense manufacturers are aggregated under NAICS material

code 325998, which is defined as other miscellaneous chemical products, manufacturers of

chemical preparations not elsewhere classified, including essential oils. This category covers

production of all types of essential oils, pyrotechnics, fireworks, drilling muds, and other

industrial preparations, such as foundry and rubber processing supplies. ERG was unable to find

a detailed source of government data covering specifically incense manufacturing and sales.

The Thomas Register of American Manufacturers on-line database lists 26 companies as

manufacturers of incense. After contacting nine of the companies listed, we were able to find

very little additional information about incense manufacturing in the US. One company

representative said that many companies listed as manufacturers may indeed be repackagers who

import incense and repackage it for sale in the US. Another stated that there are many domestic

manufacturers that are very small—possibly single individuals making incense for sale locally. 

One manufacturer contacted claimed they had $500,000 in annual sales.

The US Census Bureau data on domestic exports for 1999 show a total value of $4.6 million for

incense. This figure represents total exports worldwide. The highest percentages of exports 
18

went to Canada, followed by Mexico, the United Kingdom, and Japan. Quantities (weight) of

exports were not reported.

The Census Bureau also reports data on imports of incense to the US. In 1999, $12.4 million of

incense was imported to the US. The largest percentage of imports came from India, followed by

China, Thailand, and Japan. (See Table 5.)
19

Country of Origin Value of Imports Percent of Total

India $3,308,591 26.7

China $2,290,454 18.5

Thailand $2,178,078 17.6

Japan $1,645,833 13.3

Hong Kong $891,850 7.2

United Kingdom $549,540 4.4

Mexico $507,586 4.1

Othera $459,572 3.7

France $450,941 3.5

Vietnam $126,002 1.0

Total World $12,408,447 100 a

Countries each supplying less than 1 percent of imports, including Canada, 

The Netherlands, Belgium, Germany, Italy, Greece, Syria, Israel, Saudi Arabia, 

Pakistan, Nepal, Burma, Indonesia, Macao, Korea, Taiwan, Australia, Egypt, 

and Ethiopia.

Source: US Census Bureau

Table 5: 1999 Imports of Odoriferous Preparations Which Operate By Burning

Given that $12.4 million worth of incense is imported to the US, and $4.6 million is produced

domestically for export, the US market for incense is at least $17 million, excluding the value of

what is produced domestically for domestic consumption.

Descriptive literature on the incense industry is very limited. Only one article was found despite

a thorough search of market literature databases. This article discussed the incense

manufacturing industry in Japan. It reported that the largest Japanese manufacturer of incense is

Nippon Kodo Co. Ltd., who manufactures more than 2,000 fragrance products made from natural

materials. One-third of its annual turnover is derived from overseas markets, including Europe
20

and the US. Company officials claim they control more than 50 percent of the incense market in

the country. The company has six plants in Japan, one in Taiwan, and one in Hong Kong and

imports its raw materials from Vietnam and Indonesia. This year, the company began 

distributing incense in Malaysia to satisfy the increasing demand for environmentally friendly

incense for religious, home fragrance, and anti-stress purposes (Bernama, 2000).
21

4. POTENTIAL INDOOR AIR QUALITY IMPACTS OF BURNING 

CANDLES AND INCENSE

4.A CANDLES

When candles are burned, they emit trace amounts of organic chemicals, including acetaldehyde,

formaldehyde, acrolein, and naphthalene (Lau et al., 1997). However, the primary constituent of

public health concern in candle emissions is lead. Metal was originally put in wicks to keep the

wick standing straight when the surrounding wax begins to melt. The metal prevents the wick

from falling over and extinguishing itself as soon as the wax fails to support it. The US candle

manufacturing industry voluntarily agreed to cease production of lead-containing candles in

1974, once it was shown that burning lead-wick candles resulted in increased lead concentrations

in indoor air (Sobel et al., 2000b). Unfortunately, despite the voluntary ban, lead wick candles

can still be found on the market.

According to the National Candle Association (NCA), most US candle manufacturers have

abided by the agreement to cease lead wick production. All of the NCA members have signed

pledges not to use lead wicks in candles they manufacture. In addition, the NCA has sent a letter

to all the candle manufacturers registered with the Thomas Register of American Manufacturers

informing them of the potentially adverse health effects associated with wicks that contain lead

and asking them to sign pledges not to use wicks containing lead in their candles. The NCA has

also sent letters to retailer trade associations to inform them of this issue.

The NCA states that only a small number (one or two) of candle manufacturers make their own
22

wicks. The rest purchase wicks from wick manufacturers. One such manufacturer is Atkins and

Pearce, Inc.; they claim to have stopped making and selling wicks with lead in 1999.

The Candle Product Subcommittee of the American Society of Testing and Materials (ASTM) is

working on voluntary standards for candle content, including labeling standards. It is anticipated

that this standard will address the lead issue. The draft standard was presented at the fall 2000

ASTM meeting.

There have been limited investigations regarding the prevalence and source of candles with lead

wicks. ERG did not find any statistical studies investigating the presence of lead-wick candles in

the US marketplace. However, a handful of studies contain some information about the

occurrence of lead-wick candles in the local study areas. The following discussion and Table 6

present information on lead and other chemicals emitted from candles.

Lead Wick Emissions

In February 2000, the Public Citizen’s Health Research Group conducted a study of the lead

content of candles in the Baltimore-Washington area. They purchased 285 candles from 12

stores, excluding candle-only stores, and tested the wicks for the presence of lead. They found

that nine candles, or 3% of the candles they purchased, contained lead. Total lead content ranged

from approximately 24,000 to 118,000 μg (33 to 85% of the weight of the metal in the candle

wick).
An academic study was conducted on the emissions of lead and zinc from candles with metalcore wicks (Nriagu and Kim, 2000). For this study, the researchers purchased and tested candles

(found in Michigan stores) that had metal-core wicks. Fourteen brands of candles manufactured

in the US, Mexico, and China were found to contain lead. Emission rates from candles ranged

from 0.52 to 327 μg-lead/hour, resulting in lead levels in air ranging from 0.02 to 13.1 μg/m3

.

These concentrations are below the Occupational Safety and Health Administration (OSHA)

Permissible Exposure Limit4

 (PEL) of 50 μg/m3, but above the EPA outdoor ambient air quality

standard5

 of 1.5 μg/m3. It is important to note that, although the EPA standard was not developed

for use for indoor air comparisons, it is used throughout this report as a conservative comparison

value. OSHA’s PEL values should also be interpreted with some caution for they are

occupational standards not designed for the protection of the general public, children, or sensitive

populations.

Another prominent study, van Alphen (1999), examined emissions and inhalation exposurebased risks for candles having lead wick cores. The mean emission rate was 770 μg-lead/hour,

with a range of 450 to 1,130 μg-lead/hour. A candle burned for 3 hours at 1,000 μg-lead/hour

in a 50 m3

 room with poor ventilation is estimated to yield a 24-hour lead concentration of 9.9

μg/m3

, and a peak concentration of 42.1 μg/m3. OSHA’s 50 μg/m3 PEL is not approached in this

4

PEL (Permissible Exposure Limit): These OSHA standards were designed to provide health protection for 

industry employees by regulating exposure to over 300 chemicals. PELs are an 8-hour time weighted average. 

5

EPA Outdoor Ambient Air Quality Standards: Required by the Clean Air Act, these standards were set for

pollutants thought to harm public health and the environment, including the health of "sensitive" populations 

such as asthmatics, children, and the elderly.

23
24

study, but again, EPA’s outdoor ambient air standard of 1.5 μg/m3 is exceeded.

Sobel et al. (2000a) modeled lead emissions from candles containing lead wicks. After burning

multiple candles in a contained room, 24-hour lead concentrations ranged from 15.2 to 54.0

μg/m3

. The candle containing the least amount of lead produced lead concentrations of 30.6

μg/m3

 in 3 hours. The maximum concentration of 54 μg/m3 is above the PEL standard of 50

μg/m3

 and EPA’s outdoor ambient air quality standard of 1.5 μg/m3.

Other Metals

Zinc

After the ban on lead-containing wicks, candle companies began looking for alternatives that

provided the desired characteristics of the lead wick without the harmful emissions. Many

companies turned to braided wicks, which consist of three smaller wicks wound together to

provide some stiffness. Zinc cores are also commonly used, since the metal provides the desired

amount of stiffness, burns off readily with the rest of the wick, and does not have the same toxic

effects as lead.

Zinc is an essential element for human health. However, inhaling large amounts of zinc (as zinc

dust or fumes from smelting or welding) over a short period of time (acute exposure) can cause

a disease called metal fume fever. Very little is known about the long-term effects of breathing

zinc dust or fumes (Eco-USA.net, 2000).
25

Nriagu and Kim (2000) found the release of zinc from metal-core wicks to be 1.2 to 124

μg/hour, which is too low to be of health concern in indoor air. All nonferrous metals have

traces of lead impurities; for zinc, the maximum lead content is 0.004% (Barker Co., 2000). 

The lead emissions from zinc wicks are below the detection level of most test methods (Barker

Co., 2000), though one study found emission rates of 0.014 μg-lead/hour (Ungers and

Associates, 2000).

Tin

Tin is also commonly used as a stiffener for candle wicks. It is considered to be nontoxic

(Chemglobe, 2000). Tin has a maximum lead content of 0.08%, but, like zinc, lead emissions

are below the detection limit when tin wicks are burned (Barker Co., 2000).

Organics

Several organic compounds have been detected in candle emissions. Three articles have

focused specifically on this topic. Lau et al. (1997) measured levels of selected compounds in

candle materials and modeled human exposure to a worst-case scenario of 30 candles burned for

3 hours in a 40 m3

 room with realistic air flow conditions. Schwind and Hosseinpour (1994)

analyzed candle materials and the combustion process, and created a worst-case scenario of 30

candles burned for 4 hours in a 50 m3

 room with approximately 0.7 L/min air flow. Fine et al.

(1999) also performed a series of emission tests on the combustion of paraffin and beeswax
candles burned in an air chamber with a volume of approximately 0.64 m3

 and an air flow rate

of 100 L/min. Results of the studies are presented below and in Table 6.

Acetaldehyde

6

10-6 excess cancer risk level: This EPA comparison value is the air concentration known to produce an 

increased risk of 1 in 1,000,000 for cancer.

7

RfC (Reference Concentration): This EPA health-based comparison value assumes that there is a threshold for

certain toxic effects. The RfC is an estimate (with uncertainty spanning perhaps an order of magnitude) of a 

daily inhalation exposure of the human population (including sensitive subgroups) that is likely to be without 

an appreciable risk of deleterious effects during a lifetime. 

8

STEL (Short-Term Exposure Level): This OSHA standard was designed to limit maximum concentrations of

exposure as averaged over any 15 minute period. This is an occupational standard, not designed for the 

protection of the general public, children, or sensitive populations.

Acetaldehyde levels for 30 candles burned in an enclosed room for 3 hours were modeled at

0.834 μg/m3

 (Lau et al., 1997); this is above the EPA’s 10-6 excess cancer risk level6 of 0.5

μg/m3

, but below the EPA inhalation reference concentration (RfC)7 of 9 μg/m3.

Formaldehyde

Formaldehyde levels were measured at 0.190 μg/m3 (Lau et al., 1997) and 17 μg/m3 (Schwind

and Hosseinpour, 1994). Again, these measurements were above the EPA’s 10-6 excess cancer

risk level of 0.08 μg/m3

, but below the OSHA PEL maximum of 921.1 μg/m3. Formaldehyde

levels for both studies were far below OSHA’s STEL8

 maximum of 2,456.1 μg/m3.

Acrolein

Maximum concentrations of acrolein were measured at 0.073 μg/m3 (Lau et al., 1997) and <1

μg/m3

 (Schwind and Hosseinpour, 1994). These levels are above the RfC of 0.02 μg/m3 and

26
27

below the PEL of 250 μg/m3. A cigarette burned in a similar environment produces acrolein

levels of 23 μg/m3 (Lau et al., 1997).

Polychlorodibenzo-p-dioxins/Polychlorodibenzofurans (PCDD/PCDF)

Levels of PCDD/PCDF were measured at 0.038 pg I-TEQ/m3 (Schwind and Hosseinpour, 

1994). The TEQ is the toxic equivalency method used to evaluate dioxins. It represents the sum

of the concentrations of the multiple dioxin congeners "adjusted" to account for the toxicity of

each congener relative to the most toxic dioxin, 2,3,7,8-TCDD.

Polyaromatic Hydrocarbons (PAHs)

The amount of PAHs measured in candle emissions and soot differs between studies. Fine et al.

(1999) found that no significant levels of PAHs were detected in the emissions from normal

burning and smoldering candles. In contrast, Huynh et al. (1991) found that soot from wax-light

church candles contained measurable concentrations of PAHs: the study measured 882 μg

benzo[ghi]perylene per gram of candle soot and 163 μg benzo[a]pyrene per gram of candle soot. 

However, Huynh et al. did not measure PAH concentrations from candles in air. Wallace 

(2000) also concluded that a citronella candle was a source of PAHs in a study of real-time

monitoring of PAHs in an occupied townhouse, but did not quantify the concentration or

emission rate.

Concentrations of benzo[a]pyrene in air due to candle emissions can measure 0.002 μg/m3 (Lau 

et al., 1997). This is below the PEL value of 200 μg/m3

. Naphthalene maximum concentration
28

levels were measured at 0.04 μg/m3 (Schwind and Hosseinpour, 1994), below the EPA RfC of 3

μg/m3

.

Alkanes, Wax Esters, Alkanoic and Alkenoic Acids, Alkenes

Fine et al. (1999) found that the majority of emissions from candles consisted of organic

compounds including alkanes, wax esters, alkanoic and alkenoic acids, and alkenes. Some of 

the compounds found were thermally altered products of the unburned wax, while others were

unaltered in the volatilization process. Concentrations of the organic compounds in air were not

calculated.

Particulate Matter

The diameter of candle flame particles have been measured between 20 and 100 nm (Li and

Hopke, 1993) and 100 and 800 nm depending on the mode of burning (Fine et al. 1999). 

Neither study calculated maximum concentrations of particles in air. Li and Hopke (1993)

subjected candle flame particles to relative humidity comparable to that in the human respiratory

tract, and found that candle flame particles grew in size. White candles had a 20% larger 

growth potential than scented candles.
29

Table 6: Indoor Air Impacts of Burning Candles

Contaminant Study Maximum

Concentration STEL PEL RfC 10-6 Excess

Cancer Risk

Lead Nriagu and

Kim

3 0.02- 13.1 μg/m NA 3 50 μg/m NA NA

van Alphen 3 42.1 μg/m

Sobel et

al.(2000a)

15.2 to 54.0

3 μg/m

Zinc Nriagu and

Kim

1.2-124 μg/hour a NA NA NA NA

Tin NA NA NA NA NA NA

Acetaldehyde Lau et al. 3 0.834 μg/m NA 360,000

3 μg/m

3 9 μg/m 3 0.5 μg/m

Formaldehyde Lau et al. 3 0.190 μg/m 2,456.1

3 μg/m

921.1

3 μg/m

NA 3 0.08 μg/m

Schwind and

Hosseinpour

3 17 μg/m

Acrolein Lau et al. 3 0.073 μg/m NA 3 250 μg/m 0.02

3 μg/m

NA

Schwind and

Hosseinpour

3 <1 μg/m

PCDD/PCDF Schwind and

Hosseinpour

0.038 pg I3 TEQ/m

NA NA NA NA

Benzo [a]

pyrene

Lau et al. 3 0.002 μg/m NA 2001

3 μg/m

NA NA

Naphthalene Schwind and

Hosseinpour

3 0.04 μg/m NA 50,000

3 μg/m

3 3 μg/m NA

Alkanes, Wax

Esters,

Alkanoic and

Alkenoic

Acids,

Alkenes

NA NA NA NA NA NA

Particulate NA NA NA NA NA NA

a

This number represents an emission rate, not a concentration. A maximum concentration was not calculated for 

zinc.
30

Candle Soot 

Black Soot Deposition (BSD) is also referred to as ghosting, carbon tracking, carbon tracing, 

and dirty house syndrome. Complaints of BSD have risen significantly since 1992 (Krause,

1999).

Black soot is the product of the incomplete combustion of carbon-containing fuels. Complete

combustion would result in a blue flame, and would produce negligible amounts of soot and

carbon monoxide. Until recently, the source for the black soot in homes was unknown. 

Through interviews and recent experiments, it is now believed that frequent candle burning is 

one of the sources of black soot. The amount of soot produced can vary greatly from candle to

candle. One type of candle can produce as much as 100 times more soot than another type

(Krause, 1999). For example, elemental carbon emission rates varied from <40 to 3,370 μg/g

candle burned in a study of sooting behavior in candles (Fine et al., 1999). The type of soot may

also vary; though primarily composed of elemental carbon, candle soot may include phthalates,

lead, and volatiles such as benzene and toluene (Krause, 1999).

Scented candles are the major source of candle soot deposition. Most candle wax paraffins are 

saturated hydrocarbons that are solid at room temperature. Most fragrance oils are unsaturated

hydrocarbons and are liquid at room temperature. The lower the carbon-to-hydrogen ratio, the

less soot is produced by the flame. Therefore, waxes that have more fragrances in them produce
31

 more soot. In other words, candles labeled “super scented” and those that are soft to the touch

are more likely to generate soot.

The situation in which a candle is burned can also impact its sooting potential. A small and

stable flame has a lower emission rate than a larger flickering flame with visible black particle

emissions (Vigil, 1998). A forced air flow around the flame can also cause sporadic sooting

behavior (Fine et al., 1999). Thus, candles in glass containers produce more soot because the

container causes unsteady air flow and disturbs the flame shape (Stephen et al., 2000). Candles

that are extinguished by oxygen deprivation, or blowing out the candle, produce more soot than

those extinguished by cutting off the tip of the wick. Cutting the wick eliminates the emissions

produced by a smoldering candle (Stephen et al., 2000).

When soot builds up in air, it eventually deposits onto surfaces due to one of four factors. First,

the particle may randomly collide with a surface. Second, soot particles can be circulated by

passing through home air-conditioning filters. Third, soot can gain enough mass to become

subject to gravity. Homes with BSD often have carpets stained from soot deposition (Vigil,

1998). Finally, the particles are attracted to electrically charged surfaces such as freezers, 

vertical plastic blinds, television sets, and computers (Krause, 1999).
32

When soot is airborne, it is subject to inhalation. The particles can potentially penetrate the

deepest areas of the lungs, the lower respiratory tract and alveoli (Krause, 1999). ERG did not

find research literature on the health effects of residential exposure to candle soot.

Conclusion

Candles with lead wicks have the potential to generate indoor airborne lead concentrations of

health concern. It is also possible for consumers to unknowingly purchase candles containing

lead wick cores and repeatedly expose themselves to harmful amounts of lead through regular

candle-burning.

Lead wicks aside, consumers are also exposed to concentrations of organic chemicals in candle

emissions. The European Candle Association (1997) and Schwind and Hosseinpour (1994)

conclude that there is no health hazard associated with candle burning even when a worst-case

scenario of 30 candles burning for 4 hours in a 50 m3

 room is assumed. However, burning

several candles exceeded the EPA’s 10-6 increased risk for cancer for acetaldehyde and

formaldehyde, and exceeded the RfC for acrolein. Once again, the RfC and EPA’s 10-6 

increased cancer risk guidelines are not designed specifically for indoor air quality issues, so

these conclusions are subject to interpretation.
33

Consumers may also not be aware that the regular burning of candles may result in BSD, 

causing damage to their homes. Sooting can be reduced by keeping candle wicks short, drafts to

a minimum, and burning unscented candles.

Additional research may want to focus on gaps in the literature, such as emissions from scented

and multi-colored candles, and maximum concentrations of organics in air produced by sooting

candles.

4.B INCENSE

Several studies found associations between exposure to incense smoke and many illnesses,

including cancer, asthma, and contact dermatitis. Incense burning was found to be a contributing

factor in the occurrence of asthma for Quatar children (Dawod and Hussain, 1995), and coughing

was found to be associated with incense exposure in a study of Taiwanese children (Yang et al.,

1997). Burning incense produces volatile fragrances that, once airborne, can reach exposed skin,

causing dermatitis (Roveri et al., 1998). An elevated risk for leukemia was found in children

whose parents burned incense during pregnancy or while nursing (Lowengart et al., 1987). A

study of childhood brain tumors showed elevated risk for children whose parents burned incense

in the home (Preston-Martin et al., 1982).

From comparing mutagenic potencies of incense, formaldehyde, and acetaldehyde to Salmonella

typhimurium T102, Chang et al. (1997) concluded that incense smoke contains highly active
34

compounds with a higher mutagenic potency than formaldehyde. Sato et al. (1980) and

Rasmussen (1987) have also found that incense smoke is mutagenic to S. typhimurium TA98, TA

100, and TA104. Incense Smoke Condensates (ISCs), the particles released during incense

burning, were found to be mutagenic and/or genotoxic in the Ames test, the SOS chromotest, and

the SCE/CHO assays. The genotoxicity of certain ISCs in mammalian cells was also found to be

higher than particles produced from tobacco smoke condensates (TSCs) (Chen et al., 1990).

Interestingly, one study concluded that burning incense decreases the chances of developing lung

cancer (Liu et al., 1993). However, this study was conducted in China, where societal factors

may have influenced the results of the study. For example, people using incense may be more

well off and therefore have healthier life styles in general (Liu et al., 1993). A few studies

examined emissions of specific contaminants from incense smoke. These results are discussed

below.

Carbon Monoxide

Carbon monoxide inhibits the blood's ability to carry oxygen to body tissues including vital

organs such as the heart and brain. Symptoms of carbon monoxide exposure vary widely based

on exposure level, duration, and the general health and age of an individual. Typical symptoms

include headache, dizziness, and nausea. These 'flu like' symptoms often result in a misdiagnosis

and can cause delayed or misdirected treatment. Contact with high levels of carbon monoxide

can result in unconsciousness and death (EPA, 2000b).
35

Although Löfroth et al. (1991) found that burning incense produced sizeable amounts of carbon

monoxide (220 mg/g incense burned), the authors concluded that it is not likely to exceed EPA

regulatory standards unless the incense is burned in a very small room with very little ventilation. 

The standard used for a comparison value in the study was the EPA’s outdoor ambient air quality

standard of 10 mg/m3

. This is not necessarily the most appropriate comparison value, especially

since mg/g incense burned, not maximum indoor air concentration, was reported.

Isoprene

Isoprene is a hydrocarbon created and emitted from plants and trees during respiration, and has

also been detected in tobacco smoke and automobile exhaust. Isoprene does have genotoxic

properties (EDF, 2000).

Interestingly, the predominant exposure to isoprene comes from its formation in the human body. 

An exhaled breath contains 1-3 mg/m3

 of isoprene. Löfroth et al. (1991) concluded that 1.1 mg

isoprene/g incense burned would not result in adverse health effects. Again, maximum indoor air 

concentrations were not provided in this study.

Benzene

Löfroth et al. (1991) compared benzene emissions from the food preparation process, cigarette

smoking, and burning incense. The study found that emissions of benzene resulting from 

burning an incense cone were 440 μg/g incense burned. Löfroth et al. concluded that this
36

emission level could possibly cause an increase in indoor benzene concentrations above urban air

background levels of 2-20 μg/m3

. A maximum indoor benzene concentration was not calculated

in this study, so we cannot justifiably compare Löfroth’s value to the EPA 10-6 excess cancer risk

estimates, reported as a range of 0.13 to 45 μg/m3 (EPA, 2000a).

Musk Xylene, Musk Ketone, and Musk Ambrette

Musk xylene (2,4,6-trinitro-1,3-dimethyl-5-tertiary butyl benzene), musk ketone (3,5-dinitro-2,6-

dimethly-4-tertiary butyl acetophenone), and musk ambrette (2-methoxy-3,5 dinitro-4-methyltertiary butylbenzene) are contained in some types of Chinese incense (Roveri et al., 1998). They

are known for making skin more sensitive to light and causing irritations. When incense is

burned, airborne particles may dissolve in the upper layer of skin and allergic contact dermatitis

may arise. However, toxicity and health data for these chemicals are not available.

Particulate Matter

Burning incense was found to generate large quantities of particulate matter (Mannix et al.,

1996). Mannix et al. estimated the median diameter of particulates in aerosols to be between 

0.24 and 0.40 μm, and hypothesize that particles could deposit in the respiratory tract. Mannix et

al. did not perform a chemical characterization of compounds present in the particulate phase, but

recommend that a human exposure scenario be done. Li and Hopke (1993) also found that

incense smoke produced larger particles, in the range of 0.1 to 0.7 μm. Tung et al. (1999) found

that PM10 concentrations in Hong Kong homes were 23% higher with smoking or incense
37

burning– the mean indoor PM10 level for all homes was 78.8 μg/m3, while mean PM10 for

smoking or incense-burning homes was 96.6 μg/m3

. This is below the EPA’s national ambient

air quality 24-hour standard of 150 μg/m3

, but above the annual standard of 50 μg/m3. Chao et 

al. (1998) found that burning incense in a home with poor ventilation could result in a peak

concentration of total suspended particulates (TSPs) of 1,850 μg/m3

. In 1987, EPA began using

PM10, particles measuring 10 μm or less in diameter, rather than TSPs as the standard unit of

measure. However, before that time, the standard for outdoor TSPs in the United States was 260

μg/m3

 for a 24-hour average and 75 μg/m3 for an annual average. The concentration of

particulates found in Chao et al. (1998) far exceeds 260 μg/m3

.

Polyaromatic Hydrocarbons (PAHs)

Reports of PAHs in incense soot have been contradictory. Chang et al. (1997) did not find PAHs

in the vapor extract of incense smoke. However, Koo (1994) determined that PAH levels rose

with incense burning in a study of Hong Kong residences. Incense soot was found to contain

measurable concentrations of fluoranthene, pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene,

benzo[a]pyrene, dibenzo[def,p]chrysene, benzo[ghi]perylene, ideno[1,2,3,-cd]pyrene,

anthanthrene, and coronene (Huynh et al., 1991). Though the study established that the

maximum dust concentration corresponded with the burning of incense, maximum 

concentrations of PAHs from incense burning were not calculated.
38

Conclusion

Incense produces particulate matter that can deposit in the respiratory tract, and elevates airborne

concentrations of carbon monoxide and benzene. Incense also contains trace amounts of

chemicals suspected of causing skin irritation, and exposure to incense has been linked with

several illnesses. Incense smoke should be considered a source of indoor pollutants in rooms in

which incense is regularly burned (Cheng and Bechtold, 1995). However, the studies reviewed

measured emissions for only a limited number of incense types and brands; with the large range

of incense manufacturers and importers on the market, other incense types could differ in the

parameters examined.
39

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