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United States Office of Chemical 

Environmental Protection Safety and Pollution 

Agency Prevention August 2011

HUMAN HEALTH HAZARDS OF 

ALTERNATIVE RESIN TECHNOLOGIES 

REPLACING UREA-FORMALDEHYDE RESIN 
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TABLE OF CONTENTS

LIST OF TABLES .................................................................................................................................... 3

CONTRIBUTORS.................................................................................................................................... 4

GLOSSARY OF TERMS AND ABBREVIATIONS................................................................................................ 5

EXECUTIVE SUMMARY........................................................................................................................... 6

LEGISLATIVE MANDATE AND OBJECTIVES .................................................................................................. 8

UREA-FORMALDEHYDE (UF) RESINS........................................................................................................ 8

IDENTIFICATION OF ALTERNATIVE RESINS ................................................................................................ 11

PHENOL-FORMALDEHYDE (PF) RESINS ............................................................................................... 12

METHYLENE DIPHENYL DIISOCYANATE (MDI) RESINS ............................................................................. 14

POLYVINYL ALCOHOL/POLYVINYL ACETATE (PVA) RESINS........................................................................ 15

BIO-BASED ADHESIVES.................................................................................................................... 16

—TANNIN-CONTAINING RESINS ..................................................................................................... 17

—POLYAMIDE EPICHLOROHYDRIN (PAE)/SOY RESINS ........................................................................ 18

—CASHEW NUT SHELL LIQUID (CNSL)-BASED RESINS......................................................................... 19

MELAMINE-BASED RESINS ................................................................................................................ 19

SCAVENGERS AND ADDITIVES ............................................................................................................ 20

CONCLUSIONS ................................................................................................................................... 22

REFERENCES...................................................................................................................................... 23
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LIST OF TABLES

Table 1. Formaldehyde Exposure in the Life Cycle of UF- Bonded CWPs...................................... 9

Table 2. Alternative Resin Technologies and Selected Chemical Substances Used in Resin and 

Composite Wood Product Manufacturing..................................................................... 12

Table 3. Formaldehyde and Phenol Exposures in the Life Cycle of PF-Bonded CWPs................ 13

Table 4. MDI /pMDI Exposure in the Life Cycle of MDI/pMDI-Bonded CWPs............................. 15

Table 5. Vinyl acetate monomer exposure in the life cycle of PVA-bonded CWPs..................... 16

Table 6. Methanol exposure in the life cycle of tannin-bonded CWPs....................................... 17

Table 7. Epichlorohydrin exposure in the life cycle of PAE/soy-bonded CWPs........................... 19
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CONTRIBUTORS

Author:

Iris A. Camacho-Ramos

Office of Pollution Prevention and Toxics

Office of Chemical Safety and Pollution Prevention

Portions of this document were developed under contract with Syracuse Research Corporation 

(SRC), Inc. The following SRC staff developed the hazard information used in this report: 

Ashlee Aldridge, Christopher Janson, Justine Von Runnen, Teresa Manyin, William L. Richards 

and Joan D. Garey.
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GLOSSARY OF TERMS AND ABBREVIATIONS

ATCM Airborne toxic control measure

CARB California Air Resources Board

CAS RN Chemistry Abstracts Service Registry Number

CNSL Cashew nut shell liquid

CWP Composite wood products

EPA Environmental Protection Agency

GI Gastrointestinal

HWPW Hardwood plywood

IRIS Integrated Risk Information System

MDA 4,4’-methylenedianiline

MDI Methylene diphenyl diisocyanate

MF Melamine formaldehyde

MUF Melamine urea formaldehyde

NAF No-added formaldehyde 

NAS National Academy of Sciences

PAE Polyamide epichlorohydrin

PF Phenol formaldehyde

pMDI Polymeric methylene diphenyl diisocyanate

PPE Personal protective equipment 

PVA Polyvinyl acetate

RfC Reference concentration

TSCA Toxic Substances Control Act

UF Urea formaldehyde

ULEF Ultra low-emitting formaldehyde

μg/m3 Micrograms per cubic meter

VAM Vinyl acetate monomer
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EXECUTIVE SUMMARY

This review of the human health hazards of alternative resin technologies replacing ureaformaldehyde (UF) resin was developed in support of implementing regulations by the United 

States Environmental Protection Agency (EPA) under the Toxic Substances Control Act (TSCA). 

Under the recently established Formaldehyde Standards for Composite Wood Products Act 

(“Formaldehyde Standards Act”), EPA must establish national limits for formaldehyde emissions 

from hardwood plywood, particleboard and medium-density fiberboard.

Formaldehyde is capable of producing serious adverse effects in humans by inhalation and 

dermal exposure, especially over prolonged periods of time. Sensory irritation is the most 

frequently reported health symptom by workers manufacturing UF resins and/or composite 

wood products (CWPs), as well as by the general population that spend most of their time in 

office buildings or residential units containing UF-bonded CWPs. Formaldehyde is a human 

carcinogen, may also cause neurological effects via the inhalation route and dermatological 

effects (e.g., allergic contact dermatitis) after dermal exposure. Individuals with asthma or 

other respiratory problems may be especially sensitive to formaldehyde’s toxicity. 

UF resins are the standard adhesives used in many CWPs. Formaldehyde released from UF 

resins may present a health hazard to those who have UF-bonded wood panels in their homes 

or office workplace. Levels of exposure to formaldehyde are even greater among those who 

manufacture the UF resin or who are exposed to it during the manufacture of UF-bonded 

CWPs; thus workers are more vulnerable to formaldehyde’s toxic effects.

In this report, seven alternative resins were assessed and then compared and contrasted to

urea-formaldehyde to determine the potential for reducing formaldehyde exposure and its

adverse health effects. Some of the alternative resins have no added formaldehyde; others 

contain formaldehyde, but emissions of formaldehyde are reduced compared to UF in at least 

some stages of the product life cycle. In addition, scavengers and additives used to minimize 

formaldehyde releases from formaldehyde-based resins were evaluated. 

A summary of the key observations is presented below.

Residential and office environment

Methylene diphenyl diisocyanate (MDI)/polymeric MDI, polyvinyl alcohol/polyvinyl acetate 

(PVA) and polyamide epichlorohydrin/soy resins are considered no-added formaldehyde resins; 

thus, these resins do not release any formaldehyde in the bonded wood products. On the other 

hand, alternative resins based on phenol-formaldehyde (PF), tannin (e.g., tannin-formaldehyde, 

tannin-PF, or tannin-UF), cashew nut shell liquid (CNSL)(e.g., CNSL-formaldehyde, CNSL-PF, or 

CNSL-UF), and melamine (e.g., melamine-formaldehyde, melamine-UF) contain formaldehyde, 

but CWPs containing them are expected to have much lower formaldehyde emissions than UFbonded CWPs resulting in a reduction of the exposures to formaldehyde.
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Furthermore, among the seven alternative resins and scavengers/additives, many chemicals of 

concern to human health were identified besides formaldehyde; among the most toxic ones are 

phenol, MDI, vinyl acetate monomer (VAM), methanol, epichlorohydrin, ammonia, and 

chromium compounds. These chemicals, when contained in the final CWP, are expected to 

constitute a negligible health hazard because emissions are not expected to occupants of office 

and residential buildings. 

Workplace environment

Chemical production of UF resins and alternative resins involve the use of raw materials such as 

formaldehyde, phenol, MDI, VAM, methanol, epichlorohydrin, ammonia, and chromium 

compounds. Hot-pressing operations during CWP manufacturing increase the potential for 

worker exposures to these chemicals due to increased volatility. Workers at these life cycle 

stages are the most exposed population to these chemicals and their degree of exposure

depends on many factors, including the availability and effective use of personal protective 

equipment (PPE) and air emission control technologies (e.g., scrubbing systems) at the 

workplace. Regarding workers involved in downstream CWP manufacturing, exposures to 

formaldehyde and other chemicals of concern would be similar to those described above for 

the residential and work environment. 

The toxicity profiles of formaldehyde, phenol, MDI, VAM, methanol, epichlorohydrin, ammonia,

and chromium compounds are well characterized in the scientific literature. Human 

epidemiological data and laboratory studies in animals have reported serious adverse effects 

(e.g., respiratory, neurological, reproductive, and/or carcinogenic effects) for these chemical 

substances. Thus, EPA assessed inhalation and dermal exposures in workers involved in the 

initial stages of the life cycle where the production of polymers (resin) and the manufacturing 

of the bonded panels take place. Occupational health impacts from these chemical substances 

are reduced when feasible engineering and work practice controls (e.g., PPE) are available at 

the workplace.
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LEGISLATIVE MANDATE AND OBJECTIVES

The United States Environmental Protection Agency (EPA) is implementing regulations under 

the Toxic Substances Control Act (TSCA) to reduce exposures to formaldehyde from composite 

wood products (CWPs). On July 7, 2010, the Formaldehyde Standards for Composite Wood 

Products Act (“Formaldehyde Standards Act”) was signed into law. Under the Formaldehyde 

Standards Act, EPA must promulgate implementing regulations by January 1, 2013, that 

establish national limits for formaldehyde emissions from hardwood plywood (HWPW), 

particleboard, and medium-density fiberboard. This legislation, which adds a Title VI to TSCA, 

mirrors regulations previously established by the California Air Resources Board (CARB) for 

CWPs sold, offered for sale, supplied, used or manufactured for sale in California. The 

standards apply to CWPs in both unfinished panels and finished products that contain ureaformaldehyde (UF) resins (i.e., high-emitting formaldehyde resin). The Act also promulgates 

emission standards for CWPs made out of alternative resin technologies such as low-emitting 

formaldehyde and no-added formaldehyde (NAF) resins; these are the resins that are evaluated 

in this report.

In support of the implementing regulations, this assessment discusses the potential human 

health hazards and exposure potential of UF resins and available alternative resins across 

different stages of the life cycle process for CWPs. This analysis does not consider emissions 

from other volatile compounds inherently present in the wood (Salthammer et al., 2010).

A cost-benefit analysis will be developed for the implementing regulations as required by 

Executive Order 12866 (“Regulatory Planning and Review”). This hazard assessment will 

provide support for the economic analysis of costs and benefits.

UREA-FORMALDEHYDE (UF) RESINS 

UF resins are the standard adhesives used in the manufacture of many CWPs, such as HWPW, 

medium-density fiberboard and particleboard. UF resins are cross-linked with the wood and 

usually cured under high temperature/pressure conditions to form an adhesive which binds the 

different wood feedstocks together to form the CWPs (EPA, 2011b). Formaldehyde is released 

from UF bonded products.

UF resins are significant sources of formaldehyde emissions. There are three possible sources 

of formaldehyde emissions from CWPs containing UF resins. Free, unreacted formaldehyde can 

off-gas from the UF resin; the amount of free formaldehyde depends on the ratio of urea and 

formaldehyde added to the resin and the reaction conditions (pH, temperature, time) during 

resin formation. Formaldehyde emissions also occur while the resin is curing during the 

manufacturing process of CWPs. Lastly, exposure of CWPs to heat and humidity can contribute 

to formaldehyde releases (EPA, 2011). 
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Because CWPs made with UF resins release formaldehyde, EPA is concerned about potential 

exposures to those living in houses containing UF-resin building materials and those working in 

the CWP industry. Breathing of low levels of formaldehyde (<100 ppb) is also expected in office 

and residential buildings (e.g., commercial/consumer use) containing CWPs; therefore, the 

general population (e.g., children, adults, elderly) and office workers are also expected to be 

exposed to formaldehyde (Table 1; EPA, 2011c; EPA, 2011d). The rate of formaldehyde release 

is highest right after CWPs are manufactured and decreases rapidly after the first few months, 

reaching background levels in a few years; thus, the greatest exposure level for the consumer is 

when CWPs are relatively new. Dermal exposure is not expected to be a significant exposure 

route after UF resin and CWP manufacturing. Dermal and inhalation exposures to 

formaldehyde are expected for workers involved in the manufacture of UF resins and CWPs, 

especially in the absence of personal protective equipment (PPE) (EPA, 2011c; EPA, 2011d). 

Table 1. Formaldehyde Exposure in the Life Cycle of UF- Bonded CWPs

Chemical Substance of 

Concern

Life Cycle Stage

UF resin 

manufacturing

CWP 

manufacturing

Downstream 

product 

manufacturing

Commercial and 

Consumer Use

Formaldehyde Inhalation and 

dermal exposures are

expected.

Inhalation and 

dermal exposures

are expected.

Inhalation 

exposure is 

expected.

Inhalation exposure 

is expected.

Note: The use of CWPs in office and residential building is an example of commercial/consumer use.

Based on its toxicity profile, EPA decided to focus on formaldehyde as the chemical of concern 

for UF resins. Formaldehyde (CAS RN: 50-00-0) is a flammable, colorless gas at room 

temperature with a pungent, suffocating odor. It is a highly reactive, water soluble chemical 

that is rapidly absorbed by the respiratory tract. More than 90% of inhaled formaldehyde is 

absorbed in the upper respiratory tract. Although all tissues are capable of metabolizing 

formaldehyde, the tissues of the respiratory tract are expected to rapidly metabolize 

formaldehyde with little or no formaldehyde reaching the blood. Oral absorption is expected to 

be high, but dermal absorption is quite low. Once absorbed, formaldehyde is primarily 

metabolized by glutathione-dependent formaldehyde dehydrogenase and aldehyde 

dehydrogenases. Formaldehyde is oxidized to formate which enters various reactions resulting 

in the production of metabolic by-products such as carbon dioxide (ATSDR, 1999; IARC, 2006; 

NAC, 2008).

Sensory irritation is the effect most frequently reported in humans after inhalation exposure to 

formaldehyde. Individuals may exhibit signs of eye, nose and throat irritation after inhaling 

formaldehyde for a short time or on a continuous basis. Pulmonary function may be affected 

by repeated exposure to formaldehyde and there is evidence of increased asthma incidence 

associated with formaldehyde exposure. It is also likely that individuals with respiratory 

illnesses (e.g., asthma, respiratory allergy) will be more sensitive to the effects of inhaled 

formaldehyde (ATSDR, 1999; ATSDR, 2010; IARC, 2006). 
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Moreover, limited human studies suggest that chronic occupational exposure to formaldehyde

vapors may be associated with reproductive effects in women; however, other studies have not 

reported such association (ATSDR, 2010; NRC, 2008a). Neurological impairment has also been 

reported in people repeatedly exposed to formaldehyde vapors (ATSDR, 1999; ATSDR, 2010; 

NRC, 2008a). 

Formaldehyde has been classified as a known human carcinogen by the International Agency 

for Research on Cancer and the National Toxicology Program (IARC, 2006; NTP, 2011). In 1991, 

EPA classified formaldehyde as a probable human carcinogen and issued a quantitative 

estimate of carcinogenic risk in humans for inhalation exposures (i.e., inhalation unit risk= 1.3 x 

10-5per μg/m3). The inhalation unit risk was based on nasal squamous cell carcinomas 

observed in male rats chronically exposed to formaldehyde (EPA, 1991). 

EPA’s Integrated Risk Information System (IRIS) program is currently re-evaluating the cancer 

risks of formaldehyde as well as developing a reference concentration (RfC) for non-cancer 

effects. The latest draft IRIS assessment classified formaldehyde as carcinogenic to humans by 

the inhalation route of exposure and derived an inhalation unit risk considering human 

epidemiological evidence for several types of nasal cancer and leukemias (EPA, 2010). The 

National Research Council (NRC) of the National Academy of Sciences recently issued its review 

of the IRIS document on formaldehyde (NRC, 2011) and EPA is working on a revised 

assessment.

Health effects have been reported for individuals dermally or orally exposed to formaldehyde. 

Repeated contact with liquid solutions of formaldehyde has resulted in skin irritation and 

allergic contact dermatitis in humans. When ingested, formaldehyde solutions can cause 

severe injury to the gastrointestinal (GI) tract with signs of inflammation and ulceration of the 

mouth, esophagus and stomach (NAC, 2008). 

Urea (CAS RN: 57-13-6) is another chemical substance used in the production of UF resins. 

Urea occurs naturally in mammals as an end-product of amino acid metabolism, which is 

excreted (IPCS, 2009). It can be expected that the human organism is well-adapted to urea 

within the normal physiological range of concentrations, as well as higher concentrations

(OECD, 2002a). This is supported by clinical evidence from high-dose oral administration for 

therapeutic purposes (OECD, 2002a). The substance can be absorbed into the body by 

inhalation of its aerosol or by ingestion (ICSC, 1997); the rate of absorption via the dermal route 

is lower than that for inhalation or ingestion (OECD, 2002a). Urea is irritating to the skin, eyes 

and respiratory tract (ICSC, 1997). The acute oral toxicity is low (OECD, 2002a). Similarly, 

repeated-dose toxicity by oral and dermal routes is low (OECD, 2002a). The concern for 

reproductive and developmental toxicity is uncertain because appropriate studies are not 

available (OECD, 2002a). Urea has caused DNA single strand breaks in mammalian cells in vitro

and has been shown to be clastogenic in mammalian cells in vitro and in vivo, but only at 

concentrations well beyond the normal physiological range (about 50-100 higher than 

concentrations found in human blood); therefore, there is little concern for genetic toxicity 

(OECD, 2002a). There is no concern for carcinogenicity (OECD, 2002a). Some exposure to urea 
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may occur during the life cycle stage of UF resin manufacturing (EPA, 2011b) and significant 

human health effects are not expected due to its low hazard concern.

Methanol (CAS RN: 67-56-1) is used in the synthesis of formaldehyde, which is then used in the 

manufacture of UF resins. Occupational exposures to methanol may produce eye, skin and 

nasal irritation (CalEPA, 2000; OECD, 2004a; HSDB, 2011). Methanol exposure has been 

associated with neurotoxicity (e.g., headache, dizziness, nausea and blurred vision) (CalEPA,

2000; OECD, 2004a; NAC, 2005), metabolic acidosis (OECD, 2004a; NAC, 2005), liver and kidney 

effects (OECD, 2004a), immunotoxicity (OECD, 2004b), ocular toxicity (e.g., severe vision 

impairment and permanent blindness) (OECD, 2004a; HSDB, 2011), developmental toxicity (e.g., 

malformations, anomalies and neurodevelopmental effects) (CalEPA, 2000; OECD, 2004a; NAC,

2005; HSDB, 2011), as well as carcinogenicity (likely human carcinogen based on animal data)

(OECD, 2004a). 

Methanol emissions are not expected after the curing process of CWPs; therefore, the human 

health impact during commercial/consumer use and downstream product manufacturing 

processes is likely to be minimal because inhalation exposure is not expected at those times.

Workers continuously exposed to methanol are more vulnerable to methanol-related effects in 

the absence of PPE during the manufacturing of UF resins and CWPs. Methanol is a volatile

chemical; therefore, inhalation exposure is the most likely route, although dermal exposures to 

methanol solutions cannot be completely ruled out at the workplace. During CWP 

manufacturing, boards are generally subject to high temperatures during the curing process. 

Because methanol’s volatility will be enhanced at high temperatures, methanol exposure is

likely to be higher during CWP manufacturing rather than during the UF resin production (EPA, 

2011b; EPA, 2011c). 

IDENTIFICATION OF ALTERNATIVE RESINS 

EPA identified various alternative resin technologies that are being used to replace UF resins in 

CWPs and achieve lower formaldehyde emissions (Table 2) (EPA, 2011a; EPA, 2011b). As part 

of the development of the list of alternative resins, chemistry information was evaluated to 

understand potential exposures to certain chemical substances involved in resin manufacturing 

as well as downstream processes ranging from CWP manufacturing to commercial and 

consumer use (EPA, 2011b). The alternative resins and scavengers are consistent with what 

industry is currently using in certain CWPs to meet the CARB airborne toxic control measure 

(ATCM) limits. Moreover, this analysis considers the resin technologies subject to regulatory 

emission standards by the Formaldehyde Standards Act. For instance, the Act sets emission 

standards for CWPs containing NAF-based resins and may include resins using soy, polyvinyl 

acetate, and methylene diphenyl diisocyanate (MDI) in their composition. Similarly, the Act 

covers CWPs made out of ultra low-emitting formaldehyde (ULEF) resins and may include resins 

containing melamine-urea-formaldehyde (MUF), phenol formaldehyde (PF) and resorcinol1

formaldehyde.

 

1 Resorcinol is a phenolic resin adhesive. 
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Table 2 also lists chemical substances that are important for resin and/or CWP functionality and 

that could present a relevant source of exposure at certain stages of the product’s life cycle, 

including additives and scavengers that are added to the resin matrix to reduce formaldehyde 

emissions and/or enhance wood bonding.

Table 2. Alternative Resin Technologies and Selected Chemical Substances Used in Resin and Composite 

Wood Product Manufacturing

Type of Resin Name(s) of chemicals

Phenol-Formaldehyde (PF) resins Phenol, formaldehyde

Methylene diphenyl diisocyanate (MDI) resins MDI, formaldehyde

Polyvinyl alcohol/polyvinyl acetate (PVA) resins Vinyl acetate monomer

Bio-based resin: Tannin-containing resins Tannins, methanol, formaldehyde

Bio-based resin: Polyamide epichlorohydrin 

(PAE)-soy resins

Epichlorohydrin, soy protein

Bio-based resin: Cashew nut shell liquid (CNSL)-

containing resins

Cashew nut shell liquid, formaldehyde

Melamine-based resins 

(melamine-formaldehyde or melamine-ureaformaldehyde resins)Urea, formaldehyde, melamine

Scavengers and additives

used in alternative resins 

Urea, ammonia, phenol, tannins, soy protein, melamine, 

hexamine, sodium sulfate, sodium chloride, triacetin, 

tris(hydroxymethyl) nitromethane and chromium 

compounds. 

Note: Additives and scavengers may be used in combination with resin components to reduce formaldehyde 

emissions and enhance wood bonding.

Phenol-Formaldehyde (PF) Resins

PF resins are another major adhesive used in the CWP industry for products such as plywood,

particle board, waferboard and fiberboard (CalEPA, 2007; EPA, 2011c). Phenol and 

formaldehyde are reactants in the synthesis of PF resins. The initial reaction of formaldehyde 

and phenol occurs with excess formaldehyde; therefore, phenol is the limiting reagent and is 

expected to be consumed in the reaction (EPA, 2011b). 

While most studies indicate that PF resins have low formaldehyde emissions, this is generally 

achieved at the latter stage of curing and adhesive formation (i.e., commercial/consumer use; 

downstream CWP manufacturing). Because the initial reaction occurs using an excess of 

formaldehyde, it is assumed that phenol exposure is negligible during downstream CWP 

commercial/consumer use and manufacturing (EPA, 2011b; EPA, 2011c). Inhalation and dermal 

exposure to phenol and formaldehyde may occur during the synthetic process of the resin and 

CWP manufacturing. For instance, workers are expected to breathe phenol during various 

activities performed during PF resin manufacturing (e.g., filling, transfer, sampling, drumming, 

cleaning, maintenance and repair work). Dermal exposures are also possible, but workers 

usually wear PPE due to phenol’s corrosive properties (EPA, 2011b; EPA, 2011c; EPA, 2011d). 
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Table 3 summarizes the potential exposures to formaldehyde and phenol during the life cycle 

process of PF-bonded CWPs.

Table 3. Formaldehyde and Phenol Exposures in the Life Cycle of PF-Bonded CWPs

Chemical substance

of Concern

Life Cycle Stage

PF resin 

manufacturing

CWP 

manufacturing

Downstream product 

manufacturing

Commercial and 

Consumer Use

Formaldehyde Inhalation and 

dermal exposures

are expected.

Inhalation and 

dermal exposures

are expected.

Inhalation exposure is 

expected, but lower 

emissions are also 

expected relative to 

UF.

Inhalation exposure

is expected, but 

lower emissions are 

also expected 

relative to UF.

Phenol Inhalation exposure 

is expected. Dermal 

exposure is 

possible.

Inhalation 

exposure is 

expected. Dermal 

exposure is 

possible.

Negligible inhalation 

and dermal exposures

are expected.

Negligible inhalation 

and dermal 

exposures are

expected.

 Note: The use of CWPs in office and residential building is an example of commercial/consumer use.

Phenol (CAS RN: 108-95-2) is corrosive to the eyes, skin and respiratory tract (IPCS, 2001; OECD,

2004b). Absorption is high through the lung, skin and GI tract (IPCS, 2001; OECD, 2004b; IARC,

1989). Phenol is not expected to be a dermal sensitizer (OECD, 2004). Acute dermal toxicity is 

moderate, and acute inhalation toxicity is uncertain due to a lack of studies (OECD, 2004b; EPA,

2002). The systemic effects of dermal and inhalation exposures may be widespread and include 

liver and kidney toxicity, as well as cardiovascular effects and neurotoxicity (EPA, 2002; ATSDR,

2008). Inhalation exposure is expected to adversely affect the respiratory system (ATSDR,

2008). There is uncertain concern for developmental and reproductive toxicity via the dermal 

and inhalation routes, although reproductive and developmental effects have been observed at 

high concentrations in oral exposures (ATSDR, 2008). There is concern for genotoxicity. 

Although phenol has shown little evidence of mutagenic properties in bacterial tests, it has 

demonstrated mutagenicity and clastogenicity in testing with mammalian cells in vitro (OECD,

2004b; IARC, 1989; ATSDR, 2008). There are mixed results for testing in vivo, including some 

positive results for the induction of chromosomal aberrations and micronuclei in mice (ATSDR,

2008). The carcinogenicity of phenol is uncertain (i.e., phenol is considered non-classifiable as 

to its carcinogenicity in humans) (IARC, 1989); however, dermally-applied phenol is a cancer 

promoter (OECD, 2004b). There is concern for neurotoxicity, with effects including convulsions, 

loss of coordination, reduced motor activity and paralysis (OECD, 2004b).

Health concerns for phenol-related adverse effects are expected to be minimal during the late 

stages of the life cycle (e.g., commercial/consumer use; downstream product manufacturing) 

because individuals are not likely to come in contact with phenol (EPA, 2011c). CWPs made 

with PF resins usually have 90% less formaldehyde emissions than CWPs made with UF resins

(HBN, 2008). A 90% reduction in formaldehyde emissions means that the likelihood of adverse 

health effects is dramatically reduced for the later stages of the CWP’s life cycle (i.e., 

commercial/consumer use; downstream manufacturing). 
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As in the case of formaldehyde, the range of toxic effects for phenol makes it a chemical of 

concern in the occupational setting. Workers repeatedly exposed to both phenol and 

formaldehyde may be more vulnerable to adverse effects when working in the manufacturing 

process of PF resins and CWPs especially if exposures occur in the absence of PPE. 

Methylene diphenyl diisocyanate (MDI) resins

Isocyanate-based resins have a rapid polymerization and, because isocyanates have high 

reactivity and efficiency in bonding, they can react with many other monomers, allowing a great 

flexibility in the production of various types of isocyanate-based resins. For example, a mixture 

of aromatic monomer MDI and the associated methylene- bridged polymeric MDI (pMDI) is 

used as an adhesive for CWPs such as oriented strand board, particle board and mediumdensity fiberboard (Frihart, 2005; EPA, 2011b; EPA, 2011c).

MDI and pMDI are produced from raw materials such as formaldehyde (HBN, 2008). The 

synthesis of MDI/pMDI resins requires MDI and water to start the polymerization process. The 

isocyanate group reacts with water to form an unstable carbamic acid which is subsequently 

converted to an amine. Subsequently, self-polymerization rapidly occurs resulting in an 

oligomeric homopolymer. The polarity, viscocity and molecular weight of MDI/pMDI resins are 

low when compared to other wood adhesives and these properties cause them to rapidly 

penetrate the wood surface (Frihart, 2005; EPA, 2011b). 

Inhalation and dermal exposures to MDI/pMDI are not expected during the use of MDI/pMDIbonded CWPs (i.e., commercial/consumer use; downstream product manufacturing) due to the 

rapid reactivity of the isocyanate groups2(Frihart, 2005; EPA, 2011c) (Table 4). In the

occupational setting, the synthesis of the resin is typically done in a closed system to avoid 

unnecessary exposures to workers. Volatility of the MDI/pMDI resins is low and, although the 

resin is produced in a closed system, occupational exposures (inhalation and dermal) may occur 

during worker activities at the manufacturing stage of the MDI/pMDI resins (e.g., sampling;

equipment cleaning; accidental spill cleanup) or during the primary manufacturing of CWPs

(e.g., spraying; volatilization in hot pressing operations) (Table 4) (EPA, 2011b; EPA, 2011c; Pizzi 

and Mittal, 2003). In addition, exposures are mitigated if PPE is regularly used in the workplace

(EPA, 2011c; Frihart, 2005). 

 

2

 In April 2011, EPA issued an Action Plan addressing the use of MDI and related compounds in products that may 

result from exposures to the consumer or self-employed worker while using products containing uncured 

(unreacted) diisocyanates (e.g., spray applied foam sealants, adhesives, and coatings) or incidental exposures to 

the general population while such products are used in or around buildings including homes or schools (EPA, 

2011e). The Action Plan did not focus on MDI use in CPWs; therefore, the information cited in this document 

comes from EPA’s report entitled “Occupational and consumer exposure and environmental release assessment 

of formaldehyde in urea-formaldehyde resin manufacture and of certain chemicals for substitute technologies to 

reduce emissions from composite wood products” (EPA, 2011c), which concluded that the use of MDI resins in 

CWPs is not expected to result in consumer or general population exposure.
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Table 4. MDI /pMDI Exposure in the Life Cycle of MDI/pMDI-Bonded CWPs

Chemical substance 

of Concern

Life Cycle Stage

MDI/pMDI resin 

manufacturing

CWP 

manufacturing

Downstream product 

manufacturing

Commercial and 

Consumer Use

MDI/pDMI Inhalation and 

dermal exposures

are expected.

Inhalation and 

dermal exposures

are expected.

Inhalation and dermal 

exposures are

expected to be 

negligible.

Inhalation and 

dermal exposures

are expected to be 

negligible. 

 Note: The use of CWPs in office and residential building is an example of commercial/consumer use.

Unlike UF resins, MDI/pMDI resins are formaldehyde-free adhesives, meaning that MDI/pMDIbonded CWPs do not release formaldehyde at any stage of the life cycle. However, isocyanate 

compounds are potentially toxic, especially in the absence of adequate industrial hygiene 

practices (e.g., emission control technology such as closed systems and PPE). MDI (CAS RN: 

101-68-8) exposure is a leading cause of occupational asthma and can result in irritation to the 

skin, eyes and respiratory tract (EPA, 1998a; IARC, 1999a; HSDB, 2010a; OECD, 2003). Lung 

absorption is expected to be good, but absorption is poor via the dermal route (EPA, 1998a).

MDI is acutely toxic when inhaled, but acute dermal toxicity is low; MDI has dermal sensitizing 

potential and is a known respiratory sensitizer in humans (EPA, 1998a; HSDB, 2010a; OECD,

2003). Repeated inhalation exposure to MDI aerosols may result in adverse effects in the 

respiratory tract (EPA, 1998a; HSDB, 2010a; OECD, 2003). Moreover, there is evidence for 

genotoxicity based on observations of DNA damage, formation of DNA adducts, mixed results in 

bacterial reverse mutation assays, and induction of chromosomal aberrations in vitro (EPA,

1998a). There is no conclusive evidence for carcinogenicity, although chronic inhalation 

exposure in animals has been shown to increase the incidence of benign tumors (OECD, 2003;

EPA, 1998a; IARC, 1999a). However, 4,4’-methylenedianiline (MDA), which is a

metabolite/reaction product of MDI and formed during the first steps of the synthesis of 

MDI/pMDI resins, is classified as a known carcinogen (EPA, 1998a).

Polyvinyl alcohol/polyvinyl acetate (PVA) resins

Polyvinyl alcohol/polyvinyl acetate (PVA) resins are thermoplastic adhesives used in the 

assembly of CWPs such as HWPW. The bonding process of PVA resins basically involves 

softening or melting the polymer while in contact with the panels and allowing the joined 

structure to cool. PVA resins are generally synthesized through polymerization of vinyl acetate 

monomer (VAM). Small amounts of residual VAM (< 1%) are generally present in the PVA 

resins. The majority of PVA resins use polyvinyl alcohol as the main protective colloid and 

thickener (EPA, 2011b; EPA, 2011c; Pizzi and Mittal, 2003). 

As with MDI resins, PVA resins are formaldehyde-free adhesives and, therefore, the resins do 

not release formaldehyde in the bonded products. The moisture content of the wood, alcohol 

groups in the wood and the adhesive formulation components should provide sufficient 

reactants to consume any unreacted VAM, making it unlikely that the CWPs would contain the 

unreacted monomer. Therefore, negligible inhalation exposure is expected during 

commercial/consumer use, downstream product manufacturing and CWP manufacturing (Table 

5; EPA, 2011c). 
16 | Page

However, VAM (CAS RN: 108-05-4) is an occupational hazard for those involved in the 

manufacture of PVA resin. Because of VAM’s volatility, workers may breathe VAM during the 

synthesis of the PVA resins (EPA, 2011c; Table 5). Dermal exposures may also occur in the

workplace during PVA resin manufacturing (EPA, 2011c). Repeated inhalation exposure may 

result in absorption of harmful amounts of VAM through the lungs. Workers may complain of 

eye and upper respiratory tract irritation (ATSDR, 1992; ECB, 2000b; IARC, 1995; HSDB, 2009). 

Nasal irritation, labored breathing, lung damage and convulsions have been observed in 

rodents acutely exposed to high levels of VAM by inhalation (ATSDR, 1992; HSDB, 2009). 

Furthermore, rodents repeatedly exposed to VAM via inhalation have developed lung 

congestion and respiratory tract irritation, including respiratory distress, nasal mucosal 

metaplasia, tracheal metaplasia, bronchitis or bronchiolitis (ECB, 2000b; IARC, 1995). 

Carcinogenic effects have been observed in rats via the inhalation route (nasal carcinomas), but 

there is inadequate evidence of carcinogenicity in humans (ATSDR, 1992; HSDB, 2009). 

However, VAM is rapidly metabolized in human blood and animal tissues to acetaldehyde, 

which is both genotoxic and carcinogenic (IARC, 1995). Hazards can be mitigated by 

conforming to good industrial hygiene practices (e.g., PPE).

Table 5. Vinyl acetate monomer exposure in the life cycle of PVA-bonded CWPs

Chemical substance 

of Concern

Life Cycle Stage

PVA resin 

manufacturing

CWP 

manufacturing

Downstream product 

manufacturing

Commercial and 

Consumer Use

Vinyl acetate 

monomer

Inhalation and 

dermal exposures

are expected.

Inhalation and 

dermal exposures

are expected to be 

negligible.

Inhalation and dermal 

exposures are

expected to be 

negligible.

Inhalation and 

dermal exposures

are expected to be 

negligible. 

 Note: The use of CWPs in office and residential building is an example of commercial/consumer use.

Bio-Based Adhesives

Jones (2007) defines bio-derived resins as “materials of natural, non-mineral or non-petroleum 

based origin that can be used either in their natural state or after small modification, capable of 

reproducing the behavior and performance of synthetic resins”. The application of natural 

products as binding agents dates back to before the beginning of human civilization. 

Archaeological evidence of the earliest known use suggests that Neanderthals were creating 

adhesives from birch bark more than 200,000 years ago (Roebroeks and Villa, 2011). Starch, 

blood and collagen extracts from animal sources (Lambuth, 2003), as well as natural gums and 

plant resins, are among the identified sources of binding agents used by early civilizations. 

More recently, isolated vegetable proteins have been used in certain adhesives. Resin 

durability has been a problem for bio-based adhesives, especially under wet conditions, but 

some resins have been recently designed to have a longer adhesive working life and better 

performance under high moisture conditions (Pizzi and Mittal, 2003). There has been an 

increased interest in these “green” adhesives because their production is based on renewable 

plant materials. However, resins produced with bio-based adhesives for use in CWPs are 

generally combined with formaldehyde-based resins and therefore still release some 

formaldehyde. 
17 | Page

This report discusses resins derived from tannins, soy protein and CNSL, as they have been 

identified as alternatives to UF resins in the manufacture of CWPs. 

—Tannin-containing resins

Tannin adhesives are natural resins that are mainly phenolic in nature and can be used in the 

production of CWPs (CalEPA, 2007; EPA, 2011b). Tannins can also be used as wood additives 

(EPA, 2011b). Tannin-containing resins are similar to PF resins, with tannins substituting for 

phenol. These resins have lower formaldehyde emissions than UF resins since less 

formaldehyde is used in the initial tannin-formaldehyde reaction (Pizzi and Mittal, 2003). 

However, tannin-containing resins are more expensive to produce. In general, tannins have low 

toxicity (ECB, 2000a); therefore, there is a low concern for health effects in workers handling 

tannin extracts during the manufacture of tannin-bonded CWPs. 

Methanol can be used in the production of CWPs containing tannin-based adhesives. Methanol 

is added to tannin formulations to achieve a slower curing process and lengthen a product’s 

shelf life. Residual methanol is expected to be consumed during wood processing due to its 

high volatility (EPA, 2011b). Although methanol is volatile, exposure will be negligible for 

commercial/consumer use and downstream product manufacturing processes. Dermal 

exposure is also expected to be negligible during commercial/consumer use and product 

manufacturing, although it is possible during CWP and resin manufacturing (EPA, 2011c; Table 

6).

Table 6. Methanol exposure in the life cycle of tannin-bonded CWPs

Chemical substance 

of Concern

Life Cycle Stage

Tannin-containing

resin 

manufacturing

CWP 

manufacturing

Downstream product 

manufacturing

Commercial and 

Consumer Use

Methanol

Inhalation and 

dermal exposures

are expected.

Inhalation and 

dermal exposures

are expected.

Inhalation and dermal 

exposures are

expected to be 

negligible.

Inhalation and 

dermal exposures

are expected to be 

negligible. 

 Note: The use of CWPs in office and residential building is an example of commercial/consumer use.

As in UF resins that use methanol in UF manufacturing, the application of methanol in the 

manufacturing of tannin adhesives and tannin-bonded CWPs is not expected to produce 

adverse health effects in individuals coming into contact with tannin-bonded CWPs during 

downstream stages of the life cycle. However, methanol used in the manufacturing of tannin 

adhesives and tannin-bonded CWPs does constitute an occupational hazard concern. 

Occupational exposures to methanol may produce eye, skin and nasal irritation (OECD, 2004a;

CalEPA, 2000; HSDB, 2011). Similarly, there is evidence for numerous toxic effects including 

neurotoxicity, hepatic and renal effects, immunotoxicity, ocular toxicity, developmental toxicity 

and carcinogenicity (NAC, 2005; CalEPA, 2000; OECD, 2004a; HSDB, 2011). As with UF resins, 

health effects may occur in workers repeatedly exposed to methanol during the manufacturing 

of tannin adhesives and tannin-bonded CWPs, especially in the absence of PPE.
18 | Page

—Polyamide epichlorohydrin (PAE)/soy resins

PureBond is a formaldehyde-free, soy-based adhesive sold by Columbia Forest Products used in 

the manufacture of HWPW. The adhesive is produced by coupling polyamide-epichlorohydrin 

(PAE) pre-polymer with soy protein obtained from soy flour (EPA, 2011b). 

Compared to the hazards of formaldehyde, soy protein has low toxicity properties.

However, humans may exhibit allergic reactions, including asthma, when breathing soy flour or 

soybean dust. Similarly, skin exposure to soy flour or dust may result in dermal allergies

(Gomez-Olles et al., 2007). 

Epichlorohydrin is an intermediate chemical used in the manufacture of PAE (EPA, 2011b). 

Epichlorohydrin is expected to be fully consumed in the chemical reaction making PAE; 

therefore, it is assumed that occupational exposures to epichlorohydrin will be negligible during 

all downstream processes after PAE resin production including the formulation of PureBond, 

the use of PureBond in HWPW manufacturing, and the subsequent downstream and 

commercial use of the products (EPA, 2011c) (Table 7). Consequently, these downstream 

stages of the life cycle do not constitute a hazard concern for humans.

However, epichlorohydrin could be a serious inhalation and dermal health hazard to individuals 

working in the manufacture of PAE (e.g., unloading of the epichlorohydrin into the reactor;

reaction sampling) in the absence of good industrial hygiene practices (e.g., PPE) (EPA, 2011c)

(Table 7). Epichlorohydrin (CAS RN: 106-89-8) is highly toxic to humans by inhalation and skin 

absorption (Vincoli, 1997). Inhalation exposure results in moderate to severe irritation to the 

eyes (burns can lead to permanent damage to vision), nose, throat and respiratory tract (EPA,

2009a; OECD, 2006). This chemical is a known sensitizer via inhalation and dermal absorption 

(may produce eczema or dermatitis) (OECD, 2006; Vincoli, 1997). Repeated-dose inhalation 

may result in kidney effects and changes in nasal turbinates and a range of other symptoms, 

including headache, nausea, vomiting, abdominal discomfort and pain in the liver region, 

breathing difficulties, cyanosis, coughing, and chemical pneuomonitis or pulmonary edema

(IARC, 1999b; EPA, 2009a; OECD, 2006; Vincoli, 1997). High concentrations may cause 

depression and injury to the central nervous system (i.e., tremors; somnolence; ataxia), 

potentially leading to death (Vincoli, 1997). There is high concern for reproductive toxicity and 

the chemical is also a suspected teratogen (Vincoli, 1997). Epichlorohydrin is mutagenic and is 

carcinogenic in test animals via the inhalation route. EPA has classified epichlorohydrin as a 

probable human carcinogen (EPA, 2009a).
19 | Page

Table 7. Epichlorohydrin exposure in the life cycle of PAE/soy-bonded CWPs

Chemical substance 

of Concern

Life Cycle Stage

PAE/soy resin 

manufacturing

CWP 

manufacturing

Downstream product 

manufacturing

Commercial and 

Consumer Use

Epichlorohydrin

Inhalation and 

dermal exposures

are expected.

Inhalation and 

dermal exposures

are expected to be 

negligible.

Inhalation and dermal 

exposures are

expected to be 

negligible.

Inhalation and 

dermal exposures

are expected to be 

negligible. 

 Note: The use of CWPs in office and residential building is an example of commercial/consumer use.

—Cashew nut shell liquid (CNSL)-based resins

Cashew nut shell liquid (CNSL) is a mixture of phenolic-based compounds derived from the 

cashew nut. It contains approximately 70% anacardic acid, 18% cardol, 5% cardanol and 7% 

other phenols and less polar substances (HPV, 2006a; HPV, 2006b). CNSL is used in the 

manufacture of natural, sustainable adhesives. However, as with tannin-containing resins, 

CNSL resins are often combined with formaldehyde-based resins for use in CWPs. Nonetheless, 

they are considered to be better alternatives to UF resins due to lower formaldehyde emissions

(Kim, 2010).

CNSL is less likely than UF to present a health hazard to the general population during 

commercial/consumer use due to negligible exposure to CNSL and formaldehyde at this life

cycle stage. CNSL resin is also less likely than UF resin to present a health hazard to workers 

during downstream CWP manufacturing processes. 

Dermal exposure to CNSL is expected to be low during resin and CWP manufacturing and

diminishes with the use of appropriate PPE. Inhalation exposures are not expected due to its 

low vapor pressure. CNSL is a strong skin sensitizer in animals and humans, as well as a severe 

eye and skin irritant (NICNAS, 1996; HPV, 2006a; HPV, 2006b; ECB, 2000c; EPA, 2009b). CNSL is 

not associated with the vast array of serious adverse effects that have been reported for 

formaldehyde (i.e., lung irritation; neurotoxicity; possible reproductive effects; cancer); 

therefore the hazard concern level for CNSL is low. 

Melamine-based resins

Melamine formaldehyde (MF) resins are thermosetting adhesives made from melamine and 

formaldehyde by polymerization. These resins have a much higher resistance to water attack 

when compared to UF resins, but they are more expensive to make because of the high cost of 

the melamine. Because MF resins are expensive, urea is generally added to create melamineurea-formaldehyde (MUF) resins, which are less expensive than MF resins but still retain 

acceptable water resistance (Pizzi and Mittal, 2003; Frihart, 2005). 

Melamine (CAS RN: 108-78-1) has low inhalation and dermal toxicity (IARC, 1999c; OECD,

2002b). One advantage of CWPs made out of melamine-based resins (e.g., MF, MUF) is the 

reduced amount of formaldehyde that is emitted from the product when compared to UFbonded CWPs; therefore, low exposure to formaldehyde is expected during downstream life
20 | Page

cycle stages (i.e., commercial/consumer use and during product manufacturing). Exposures to 

melamine and urea are also minimal during the production of CWPs and subsequent life cycle 

stages. 

Workers making MF and MUF resins are potentially exposed to melamine, urea and 

formaldehyde (e.g., while mixing the chemicals) (EPA, 2011c) especially in the absence of good 

industrial hygiene practices (e.g., PPE). Melamine is not expected to be an occupational irritant 

and dermal sensitizer and urea has low toxicity. However, hazard concerns for formaldehyde 

are present during the manufacture of MF and MUF resins as well as MF- and MUF-bonded 

CWPs (e.g., application of the resin; press operations) where exposures to formaldehyde vapors 

are possible. Exposure to formaldehyde vapors is associated with various adverse health 

effects, including cancer, in workers. 

Scavengers and additives

Various chemicals are used to minimize formaldehyde release from formaldehyde-based resins. 

Formaldehyde scavengers can be added to resins or directly to wood panels. It is important to 

note that the action of scavengers may be reduced in the finished CWPs over time such that 

formaldehyde exposures may increase if the product is subjected to heat and humidity (Frihart 

et al., 2010). Additives are sometimes added to resins or panels to enhance desirable 

properties (e.g., panel strength; water and mold protection) (Frihart, 2005). Scavengers and 

additives that may be added to the resin technologies discussed in this report are urea, 

ammonia, phenol, tannins, soy protein, melamine, hexamine, sodium sulfate, sodium chloride, 

triacetin, tris(hydroxymethyl) nitromethane and chromium compounds (EPA, 2011a). It is 

expected that these scavengers and additives react with components of the resin and/or wood 

panel such that chemical releases are likely to be minimal after production of the bonded 

panels. Therefore, exposure to these chemicals is not expected during commercial/consumer 

use and downstream product manufacturing. 

Dermal and inhalation exposures in the workplace are likely during resin manufacturing and 

production of CWPs. While most of these scavengers and additives have low toxicity (e.g., urea, 

melamine, hexamine, sodium chloride, sodium sulfate, soy protein, tannins, triacetin [glycerol 

triacetate] and tris [hydroxymethyl] nitromethane), there is a concern for occupational hazards 

to ammonia, phenol and chromium (III) salts. 

Wood-based panels can be treated in special chambers with a nitrogen-containing 

formaldehyde scavenger, such as ammonia (CAS RN: 7664-41-7). Ammonia can cause severe 

irritation and burning to the skin, eyes, oral cavity and respiratory tract (particularly mucous 

surfaces) immediately upon contact due to the rapid conversion of ammonia to ammonium 

hydroxide, which is very caustic. Inhalation at high concentrations can cause pulmonary edema 

and reduced pulmonary function (ATSDR, 2004; NRC, 2008b; OECD, 2007; ECB, 2000d). 

However, ammonia exposures are not expected to be significant during commercial/consumer 

use and downstream product manufacture. Although nitrogen-based scavenger additives (e.g., 
21 | Page

ammonia) with low molecular weight have high volatility in their neat form and may have the 

potential to diffuse from the wood matrix in the final product, once the additives react with 

formaldehyde, as intended, the corresponding adducts are likely to bind irreversibly to the 

wood chemical moieties. Therefore, exposures of residual ammonia are expected to be 

negligible for these life cycle stages (EPA, 2010b; EPA, 2011c). 

Ammonia does constitute an occupational hazard due to its corrosivity and irritant properties. 

Because the CWPs are usually sprayed with ammonia in a closed system, workers are unlikely 

to be exposed to high concentrations of ammonia gas via inhalation. However, some ammonia 

may remain in the treated panels and, due to its high volatility, workers may be exposed by 

inhalation. Dermal exposure is unlikely to be a significant exposure route. In the absence of a 

closed system and PPE, inhalation exposure to ammonia is expected in the workplace. 

Chromium (III) salts (e.g., chromium nitrate) are used as additives in PVA resins to improve 

water resistance. Exposures are not expected during commercial/consumer use and 

downstream manufacturing. However, Cr (III) ions are present in treated panels and have the 

theoretical ability to leach out. While there is no evidence that such leaching or migration 

occurs, if the Cr (III) salt were to leach out, it could potentially convert to the Cr (VI) oxidation 

state (hexavalent chromium) (EPA, 2011b; EPA, 2011c). Under this unlikely scenario, 

hexavalent chromium salts would constitute a prime health hazard. EPA has classified 

chromium (VI) as a known human carcinogen by the inhalation route (EPA, 1998b).

Chromium (III) nitrate solution is not expected to be volatile. Therefore, only dermal exposures 

are likely during resin and CWP manufacturing. Chromium allergic dermatitis is the major 

immunological effect of chromium (III) and is typically elicited by dermal contact in sensitized 

individuals; however, initial sensitization may result from inhalation, oral or dermal exposure or 

from a combination of these exposure routes (Langård, 2001). 

Phenol can also be included in the category of scavengers and additives. Once reacted, phenol 

is not expected to be released during commercial/consumer use and downstream product 

manufacturing. However, phenol constitutes an occupational hazard due to its corrosive 

properties as well as its adverse effects in the respiratory tract (IPCS, 2001; OECD, 2004b). GI 

effects and liver toxicity have also been reported in chronically exposed humans (ATSDR, 2008). 

There is a concern for worker inhalation and dermal exposures to phenol when used as an 

additive to CWPs at the upstream stages of the life cycle (i.e., resin and CWP manufacturing). 
22 | Page

CONCLUSIONS

UF resins are one of the most common adhesives used in the CWP industry. These adhesives 

have good bonding properties and are inexpensive to manufacture, but they are a source of 

formaldehyde emissions. CWPs made with UF resins typically release formaldehyde during the 

life of the product, but the rate of release is highest right after CWPs are manufactured and 

decreases rapidly after the first few months, reaching background levels in a few years. 

Formaldehyde constitutes a human health hazard for workers manufacturing UF resins and 

CWPs, as well as for office workers and general population that spend most of their time in 

office buildings or residential units containing UF-bonded CWPs. Sensory irritation is the most 

frequently reported health symptom and it usually disappears once the person is removed from 

the source of exposure. Individuals with respiratory problems (e.g., asthma, respiratory 

allergies) are likely to be more sensitive to formaldehyde and their symptoms may worsen 

during exposure. Formaldehyde is a respiratory carcinogen and may also cause neurological 

and reproductive effects.

Formaldehyde’s serious adverse effects in humans have contributed to the existing efforts to 

reduce or eliminate formaldehyde emissions from CWPs, including the development of new 

alternative resin technologies, which were discussed in this report. The alternative resins

evaluated in this report release either no formaldehyde or lower levels of formaldehyde than 

UF resins as a result of reformulating the resin polymer, scavenging excess formaldehyde during 

polymer production with various chemicals or a combination of both. 

Reductions in formaldehyde emissions translate into reduced hazards for workers and the 

general population using CWPs that have been bonded with alternative resins, especially during 

the late stages of the product life cycle (e.g., downstream product manufacturing and 

commercial/consumer use).

Health concerns exist for workers involved in the initial stages of the life cycle where the 

production of polymers (resin) and the manufacturing of the bonded panels take place. 

Formaldehyde, phenol, MDI, VAM, methanol, epichlorohydrin and ammonia are all resin 

components of concern. Heating of products containing resins increases the potential for 

worker exposures because it raises the vapor pressure of chemicals during hot pressing 

operations. In addition, many hot pressing methods cause other chemicals to be entrained in 

the steam from the presses. Health impacts from these chemical substances are reduced when 

feasible engineering and work practice controls (e.g., PPE) are available at the workplace.
23 | Page

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