Is Wolmanized wood safe around people, plants, and pets?

Conrad Forest Products

Wolmanized wood has a history of 60 years of safe use.

Most concerns about treated wood arise from confusion between the preservative and the preservative-treated wood.

In laboratory tests, in garden and vegetable studies, in investigations of playground structures, in surveys of carpenters and treating plant workers, and in other research conducted by various organizations, CCA-treated wood has been shown to be harmless when used as recommended.

EPA conducted an 8-year examination and determined that benefits outweighed risks. The agency recommended only modest precautions, nearly all of which also apply to untreated wood. (See the Consumer Information Sheet.)

Wolmanized wood has been used for decades for tomato stakes, grape stakes, mushroom trays, planter boxes, and bird houses with no known adverse effects. It is used in national parks, botanical gardens, and wildlife sanctuaries.

Effects of Chemical Preservatives on the Health of Wood Treating Workers in Hawaii

F.I. Gilbert, M.D.; C.E. Minn, M.S.P.H.;
R.C. Duncan, PhD.;
T. Aldrich, M.S.P.H.; W.H. Lederer, PhD.;
J.E. Wilkinson, M.S.
Pacific Health Research Institute, 1981

Cohort-Comparison Health Examination

The study cohort consisted of 66 men currently employed as wood treaters for at least the three months prior to examination and 22 men who had worked at least 12 months as wood treaters since 1960, had at least 3 months continuous service, and were currently not wood treaters. Fifty-eight matched controls and three unmatched controls were chosen of similar age (+/- 5 years), race, sex, weight (+/- 10 lbs) and level of physical activity. Controls were chosen from friends of wood treaters or from members of other craft or industrial unions. Matched controls were not found for thirty study cohort members.

Examination included a nurse interview on work history, pesticide exposure, reproductive history, recent (one year) health history and personal lifestyle habits. Physiological tests included height, weight, blood pressure, pulse, respiratory rate, skinfold thickness test, hearing test, visual acuity, peripheral and color vision and tine test for tuberculosis. Clinical laboratory tests included a complete blood count, biochemical profile and a urinalysis. A physical and neurological examination was conducted by the project physician and a first morning voiding urine was examined for levels of arsenic, copper, chromium, penta and tin. Each examinee had completed at home two general health questionnaires and a seven day diet and medication report.

Eighty-eight of the men known ever to have worked as wood treaters in Hawaii between 1960 and 1981 participated in this study. The other 94 included those who died (6), left the island (15), were unavailable (42), refused (31) or did not meet the criteria. The duration of wood treating employment was from 4 months to over 26 years with a median of 6.5 years. Thirty-three of the 88 workers had over 10 years employment. Urine pesticide residue studies found greater penta levels in the wood-treater group than in the controls, no detectable tin levels in any sample and no statistically significant difference between the groups in levels of the other metals. Urinary chromium levels were above laboratory norms for both groups. Urine arsenic levels were lower for white treaters than for others, and urine penta levels were higher for non-white treaters than for others.

The authors report significant differences between treaters and non-treaters in serum protein levels, heart rate, systolic blood pressure, left eye pressure and skinfold thickness at the scapula. Treaters and non-treaters did not differ in reproductive history (number of children fathered), recent health history, physical or neurological findings, with the exception that treaters more frequently reported stiffness or welling in the joints (25 percent vs. 9 percent).

Special analyses of specific findings versus pesticide residue levels found no associations.

The authors concluded that review of all organ systems and laboratory data showed no clinically significant differences between exposed and nonexposed cohorts. 

Historical Prospective Mortality Study and Cancer Morbidity

The 12 men who had ever been employed in the Hawaiian wood treating industry for at least three months during the period January 1960 to November 1981 constituted the study population. The 88 who participated in the clinical study in 1982 were obviously alive in November 1981. Additionally, 31 responded to the study inquiry but declined to participate, 15 had moved off the island of Oahu but were known to be alive, 11 could not be contacted although they were reported as living, six were known to be dead and for 31 there was no information. Records for 125 of the 182 wood treaters were available for the 21 year period, for whom the authors calculate eight deaths would have been expected. These deaths would have included 4 from cardiovascular causes, 3 from cancer and 1 of other causes. In fact, six deaths were known five from cardiovascular causes and one of unknown causes in the Philippines.

Three cases of cancer were known, one of bladder cancer and two of colorectal cancer. The ages at time of diagnosis were 56, 63 and 73, respectively.

The authors conclude that this study indicated no adverse health effects or increased incidence of mortality resulting from exposure to wood preservative chemicals in the treatment workers evaluated.

Carpenter Study

Pacific Biomedical Research Center, 1977

In Hawaii, where over 45,000 homes had been built almost entirely of Wolmanized wood, a study was conducted by the Pacific Biomedical Research Center of the University of Hawaii to determine any possible effect on the health of carpenters. The study covered periods both before and after Wolmanized wood was introduced in Hawaii. The authors of this study conclude that exposure to dust from such wood is not associated with increased risk of total cancer, lung cancer or lymphatic cancer. These data, which constitute the best epidemiological evidence available on treated wood, clearly show that excess respiratory cancer mortality was not observed in the carpenters exposed to arsenically-treated sawdust. In fact, OSHA has acknowledged this difference between inorganic arsenic and the arsenate compounds found in treated wood. OSHA notes:

"In the Budy-Rashad study, the carpenters were not exposed to pentavalent arsenic, but rather to a stable arsenic-wood complex. Thus, carpenter exposure to this arsenic-wood complex cannot be considered a priori equivalent to exposure to unbound pentavalent arsenic. "  (43 Federal Register 19,599 - May 5, 1978)

Raised Bed Garden Study

Hickson Corporation, 1992

Three raised bed structures were constructed: one built with untreated wood, one with Wolmanized wood and one with Wolmanized Extra water repellent lumber. These structures were divided into individual compartments, 8.5" x 10.5" and 5.5" high, so that the bottom and all sides of each compartment were of the same material.

Various vegetables were planted in the structures. After 12 weeks, the vegetables were harvested and portions were analyzed for CCA components. Vegetables obtained from a local grocery store were also analyzed.

All vegetables, including those grown in untreated compartments and those purchased in a store, contained minuscule amounts of each CCA element that were well within accepted parts per million limits.

Vegetable Analysis, Dry Basis, mg/kg (parts per million)

Vegetable Untreated Wood Wolmanized Wood Wolmanized Extra Wood Store Purchase


Carrot 3.5 1.5 1.9 1.3
Okra 1.2 1.1 0.2 -
Pepper 0.5 0.9 0.9 -
Cucumber 1.9 1.2 0.5 -
Tomato 1.1 0.4 3.5 0.6


Carrot 11.8 9.3 9.6 3.6
Okra 5.1 5.1 2.7 -
Pepper 6.9 3.8 0.5 -
Cucumber 4.2 9.5 5.1 -
Tomato 3.4 7.8 0.5 6.2


Carrot <0.8 2.2 2.9 2.7
Okra <0.8 <0.8 1.5 -
Pepper <0.8 0.5 <0.8 -
Cucumber 0.5 <0.9 <0.5 -
Tomato <0.8 0.5 2.1 3.7

Preservative Depletion

Dr. Calvin Finch and Dr. Frank Dainello, 1992

Dr. Calvin Finch, a County Cooperative Extension agent from Bexar County, Texas, and a supporting Vegetable Specialist, Dr. Frank Dainello, conducted independent research to determine if treated landscape timbers, varying in usage from 6 months to 9 years, were leaching any preservatives into the soil in raised garden beds. Along with four local Bexar County Master Gardeners, they collected soil samples from raised garden beds constructed with treated timbers of various ages in nine separate gardens in San Antonio. Twelve samples were collected 1 inch from the treated wood, 6 inches deep in the garden, and 3 samples were collected 12 inches from the timber, 6 inches deep. Ten of the samples were sent to Texas A&M's Texas Agricultural Extension Service Soil and Plant Analysis Laboratory. Five of the samples were sent to Southwest Research Institute.

Texas A&M's laboratory used a lab technique described by Dr. Larry Unruh as "a measure of water-soluble arsenic." Southwest Research Institute used a technique called the SW-846 3051 digestion method and analyzed the samples for arsenic by graphite furnace atomic absorption spectroscopy. Texas A&M's laboratory found levels of water-soluble arsenic varying between 1.1 and 4.1 parts per million (ppm) in the samples taken 1 inch from the treated timbers. In samples taken 12 inches from the timbers, 2.1 to 4.8 ppm arsenic were found.

The methods used at the Southwest Research Institute laboratory detected 3 times as much arsenic in the samples taken from the same gardens as those provided to Texas A&M . However, the levels detected (6.2 to 14 ppm) are well within the normal range of 1-20 ppm for all soils. Since the levels of arsenic found in soil samples 1 inch from the wood to 12 inches from the wood were nearly the same, Finch and Dainello concluded that the arsenic detected in the samples came from the soil and not the timbers. Further, they found no trend showing an increase or decrease of arsenic in relationship to the age of the timbers. According to Finch, "The results make me confident that CCA-treated timbers are safe to use for raised-bed vegetable gardens."

Uptake by Grape Plants of Preservatives From Pressure-Treated Posts Not Detected

M.P. Levi, D. Huisingh, W.B. Nesbitt, 1974

Leaf and stem tissue and fruit of grape plants (Vitis rotundifolia Michx. cv. Magnolia) were analyzed for copper, chromium and arsenic, 1, 2 and 3 years after planting 3 inches from copper chrome-arsenate or flour-chrome-arsenate-dinitrophenol-treated Southern pine posts. Quantities of copper in leaf and stem tissues and fruit of plants next to posts treated with copper-containing preservatives ranged from 4.9 to 10.5 ppm dry weight. The range in copper content in plants next to non-copper-treated posts ranged from 4.7 to 11.6. In all samples, chromium and arsenic contents were below 0.2 and 0.05 ppm, respectively, the limits of detection for the analytical methods used. Thus, no evidence was found suggesting uptake and translocation of wood preservative components into the leaf and stem tissue and fruit of plants from adjacent treated posts.

Estimated Risk of Skin Cancer from Dislodgeable Arsenic of Pressure Treated Wood Playground Equipment

Consumer Product Safety Commission, 1990

As part of the 1990 Playground Equipment Handbook project, a study was undertaken by the Health Sciences (HS) staff to estimate the risk of skin cancer from dislodgeable arsenic on pressure-treated wood playground equipment.

Arsenic has been associated with human skin cancer when chronically ingested. The wood preservative used in most of the U.S. wood playground equipment is chromated copper arsenate (CCA). Prior to this study, inadequate data and procedures existed for assessing the cancer risk to children playing on pressure-treated wood playground equipment as indicated by the Environmental Protection Agency (EPA) (1981, 1984) and the California Department of Health Services (1987).

Leaching experiments by HS staff demonstrated that arsenic can be released from pressure-treated wood. Seven playground equipment wood samples were collected by CPSC field staff from major U.S. manufacturers. One comparison sample of unfinished pressure-treated wood was purchased at a retail store. A method was developed by HS for testing dislodgeable arsenic on the eight wood samples.

The estimated risk of skin cancer for the five out of seven samples from manufacturers which were below the detection level of dislodgeable arsenic, was less than 1 in a million, which is a negligible risk. The estimated risk for the two out of seven samples that had detectable levels was 3-4 in a million. This is a small risk that should be reduced further if it can be practically accomplished.

The estimated risk for the comparison sample was somewhat higher (8-9 in a million). This suggests that a possible hazard might be created when playground equipment is built with unfinished pressure-treated wood from retail sources. (Note: the comparison sample was rough sawn lumber which is not acceptable for playground equipment according to AWPA standard C17.)

Evaluation of Risk to Children Using Arsenic-Treated Playground Equipment

Consumer Product Safety Commission, 1990

A report to the California State Department of Health Services; Consultants in Epidemiology and Occupational Health, Inc., 1984 Data collected by the California State Department of Health Services (DOHS) indicate that arsenic can be transferred from the surface of CCA-treated wood by rubbing with either tissues or the hands. The potential risk to children from licking their hands after playing on playground equipment built with CCA-treated materials can be calculated and compared with other exposures and risks. Analysis of the scientific data in published and unpublished studies lead the authors to the following conclusions:

  1. It appears that the maximal Arsenic (V) exposure estimate for children from use of playground equipment is within the normal variation of Arsenic (V) exposure for children;
  2. The maximum estimate of the skin cancer risk associated with such exposure approximates the skin cancer risk from the sunlight experienced during the play period;
  3. The scientific studies upon which the association of Arsenic (V) and skin cancer is based are weak; and
  4. Finally, the sampling methodology used to measure the potential exposure from wood products is uncertain with little reproducibility by individual samplers or between investigators.

A Study of Wood Preservative Leachates from Docks in an Estuarine Environment

South Carolina Department of Natural Resources
Marine Resource Division, 1995

This study examined the concentrations and biological effects of certain metals and organic compounds typically found in wood preservatives used to protect dock pilings, bulkheads, and other wooden structures from decay. The study focused on leachates from private docks in South Carolina macrotidal creek systems. Copper, chromium, arsenic, and polynuclear aromatic hydrocarbons (PAHs) were measured in composite samples of surficial sediments and naturally occurring oyster populations (Crassostrea virginica)  from creeks with high densities of docks, and from nearby reference creeks with no docks. Sediments from all but one site had metal and total PAH concentrations which were below levels reported to cause biological effects. Solid phase Microtex® bioassays using whole sediments and rotifer bioassays using sediment pore water showed no significant differences in acute toxicity between creeks with and without docks. Oysters growing directly on dock pilings had significantly higher concentrations of copper than oysters growing at least 10 m away; however, there was no significant difference in the physiological condition of these oysters. Four-day field bioassays measuring percent survival of mummichogs (Fundulus heteroclitus),  mud snails (llyanassa obsoleta),  juvenile red drum (Sciaenops ocellatus),  and juvenile white shnmp (Penaeus setiferus)  showed no significant differences between sites near to and distant from newly constructed docks. Hatchery-reared oysters showed no significant differences between dock and reference sites in percent survival, growth, or bioaccumulation of metals after six weeks of exposure. Our results suggest that, in macrotidal estuarine environments, wood preservative leachates from dock pilings have no acutely toxic effects on four common estuarine species, nor do they affect the survival or growth of juvenile oysters over a six-week time period. In some cases, metal leachates may accumulate in sediments and oysters immediately adjacent to pilings, but do not appear to become concentrated in sediments or oysters elsewhere in the same creeks.

Sediment Bound-CCA-C Leachate-10 Day/Repeated Exposure Toxicity to Ampelisca abdita & Under Static Conditions

Springborn Laboratories, Environmental Sciences Division, 1993

Leachate obtained during a 28-day period from CCA-treated and untreated pilings was dosed onto two sediment types: low organic carbon (LOC) (less than 1%) and high organic carbon (HOC) (greater than 4%). Ampelisca abdita groups were exposed to sediment of each type dosed with one of three concentrations of leachate (10%, 50% or 100% leachate). The 10-day exposure was maintained under static conditions with continuous lighting to provide maximum exposure. Survival of the organisms during the 10-day exposure period was the biological endpoint used to establish the effects of exposure.

Analyses established that copper bound to both the LOC and HOC sediments remained bound and did not desorb into the interstitial or overlying water. Analysis showed that little or no chromium was released from treated pilings over 28 days. Uptake of chromium into the LOC sediment was neglible and only a minimal amount of chromium adsorbed to the HOC sediment. Chromium in the sediment generally did not move into interstitial water but did move into overlying water from both sediments. Approximately 59.5 mg arsenic/m2 of treated wood surface area leached from the treated pilings, but arsenic did not appear to adsorb onto either sediment type, and in almost all cases, did not move into interstitial or overlying water.

Finding that leachate from untreated pilings had a greater adverse effect on organism survival than leachate obtained from CCA-treated wood pilings, the study's author concluded that the primary constituents of the CCA-treated wood pilings were not present in the leachate at concentrations which would adversely affect the survival of the organisms. (Note: The adverse effects observed with leachate from untreated pilings were presumed due to naturally occurring compounds present in untreated wood, which the author hypothesized were extracted or altered in the treatment process.)

Environmental and Occupational Health Aspects of Using CCA-Treated Timber for Walking Track Construction in the Tasmanian Wilderness World Heritage Area

M. Comfort, Tasmanian Parks and Wildlife Service, 1993

The effects of CCA-treated timber used for an extensive network of raised walkways or walking "tracks," on a pristine Tasmanian wilderness environment were evaluated. Three biophysical studies were conducted: soil sampling to determine whether leaching of chemicals was occurring, a field experiment examining whether CCA-treated sawdust affects the soil invertebrate population, and analysis of the germination rates of plants grown beneath a layer of CCA-treated sawdust.

Analysis of the soil samples revealed that minimal leaching of the chemicals from CCA-treated timber occurred. Although some values for the concentrations of copper and chromium were above background levels, none reached contamination levels set by Australian standards. The CCA elements had not moved far from the track and concentrations of CCA elements decreased with increasing soil depth.

The study suggested that the presence of CCA-treated sawdust after six months may have reduced the total number of invertebrates, but that impact was determined to be very localized. Vegetation productivity did not appear to be affected by the CCA timber track structures, and CCA-treated sawdust did not affect the germination rates of Leptospermum scoparium in a glass house trial.