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Trace Metal and Pesticide Exposure in Tree Planting in British Columbia

RS2005-OD05

Final Report Date: May 2009

Principal Investigators: Ernst Stjernberg (FERIC), and Hugh W. Davies (UBC)
Co-Investigators: Christian Van Netten (UBC)

For more information about this project, please contact Ernst Stjernberg or Dr. Hugh Davies.

View report

Disclaimer

Issue

Concerns about the health effects of occupational exposure to fertilizers have been raised by both tree planters and contractors.  Fertilizers, which sometimes contain heavy metal contaminants, are often applied at the same time that tree seedlings are planted.  Some seedlings are also treated with chemical insecticides and fungicides in the nurseries, and it is possible that there could be pesticide residues on the seedlings when they are being planted.  The purpose of this study was to examine these potential exposures and to investigate potentially related health effects.

Key findings

  • The exposure assessment did not find evidence of increased exposure to heavy metal based on air, blood or skin samples. However some tree planters were found to have been exposed to pesticide residues present on the skin (dermal exposure) while handling seedlings.
  • Tree planters’ use of personal protective equipment was inconsistent and field hygiene facilities were usually unavailable. These factors increase the risk that chemicals contaminating the skin could be ingested while eating, drinking or smoking.
  • The health effects study found that chronic respiratory symptoms, nose bleed and skin irritation were related to working with fertilizers. Workers exposed to fertilizer had a higher prevalence of most symptoms compared with unexposed workers, and the risk of some symptoms was associated with the number of days tree planters had worked with fertilizer.
  • The researchers recommend increasing worker awareness, and improving worker hygiene facilities and dermal protection, and controlling and monitoring exposure to fertilizers.

Objectives

  • To characterize tree planter exposure to fertilizers and their heavy metal contaminants, and to pesticide residues
  • To investigate potentially related health effects

Methods

Exposure Assessment
Five tree planting sites (3 in the B.C. interior and 2 in coastal B.C.) were recruited to participate in the study.  Fifty-four individuals (about ten per worksite) took part. 

Participants were monitored for airborne dust and heavy-metal exposure.  Blood samples were taken and analyzed for heavy-metals, and skin wipes were taken and analyzed for metals and pesticide residues.

Stem and foliage samples were analyzed for pesticides, and rootballs were analyzed for heavy metals.  Bulk soil and bulk fertilizer samples were both analyzed for metals.

Health effects study
A total of eleven B.C. and two Alberta tree planting work crews participated in the health effects study.  Interviews were conducted with 223 tree planters, with questions about respiratory health symptoms, dermal health, and work history.  

Interview responses were entered and analyzed using statistical software. Work-related symptoms examined in the analysis included nasal symptoms, phlegm, cough, skin irritation, and nose bleed. Exposure to fertilizer over the previous two years was estimated using the total number of days worked on contracts where fertilizer was used.

Results

Exposure Assessment

  • There was no evidence of increased exposure to heavy metal based on air, blood or skin samples, and levels of exposure to metals were generally low. Exceptions appeared to be related to other causes such as previous work experience or cigarette smoking, but not to contact with fertilizer.
  • Tree planters working in Coastal B.C. during spring planting were found to have been exposed to pesticide residues present on the skin (dermal exposure) while handling seedlings.
  • The use of personal protective equipment was found to be inconsistent and appeared to be more influenced by ergonomic considerations than by chemical exposure protection considerations. The majority of tree planters in the study used only gardening gloves, which would not provide a full chemical barrier.
  • Field hygiene facilities were usually unavailable, increasing the risk that chemicals contaminating the skin could be ingested while eating, drinking or smoking.

Health effects study

  • Nasal symptoms (including sneezing and stuffy nose) were reported by 36% of participants, and work-related phlegm, cough and skin symptoms by 16%, 14% and 11% respectively.
  • When compared with other groups of workers in two previous studies, tree planters were found to have a higher prevalence of some symptoms.  They had higher rates of cough, phlegm and nasal symptoms than participants in a study of B.C. ferry workers, and a higher prevalence of cough and phlegm than entertainment industry workers in a study of theatrical smokes and fogs.
  • Work-related cough, phlegm, wheeze, nosebleed, eye irritation and skin symptoms were more prevalent in the fertilizer exposed group than the unexposed group.  Only work-related nasal symptoms were less prevalent in the exposed group.
  • For tree planters with the highest exposure category (82 days or more of fertilizer use in the past two years) there was an increased risk for all symptoms. However, this was statistically significant only for work-related phlegm.
  • The risk of work-related cough and phlegm increased with greater fertilizer exposure. For work-related nose bleed and work-related skin irritation, there was a slightly increasing risk associated with each additional day of exposure.

Conclusions

The exposure assessment findings demonstrate the potential for tree planters to be exposed to pesticide residues, but did not find evidence of heavy metal contamination by fertilizers.  Poor hygiene practice and inconsistent use of personal protective equipment were also observed.

The health effects study findings suggest that chronic respiratory symptoms, nose bleed and skin irritation are related to working with fertilizers among tree planters. The long term health effects of this exposure are unknown.

Based on these findings, the researchers recommend the following:

  • Improve tree planter awareness of the risks of workplace chemicals
  • Improve worker hygiene facilities so that tree planters can wash their hands during the day
  • Develop a suitable dermal protection program
  • Implement exposure control measures for tree planters working with fertilizers
  • Monitor exposures to fertilizer dust and ammonia

Future directions

Further investigation of chemical exposures among tree planters is warranted, in light of the prevalence of respiratory symptoms among tree planters, and the finding of a relationship between fertilizer exposure and chronic respiratory symptoms.

Publications and Presentations

Gorman, Melanie. Assessment of chemical exposure and self-reported health among tree planters in British Columbia. Master of Science – MSc Thesis. Occupational and Environmental Hygiene, University of British Columbia.  2008.

Gorman, Melanie. Occupational Exposure to Fertilizers, Fertilizer Contaminants and Pesticides in B.C. Tree Planters: Presented at the Western Silvicultural Contractors' Association 2008 Conference and Trade Show. Sun Peaks, BC, February 2008.

Gorman, Melanie. Heavy Metal and Pesticide Exposure in B.C. Tree Planters. Presented at the University of British Columbia School of Environmental Health Seminar Series. Vancouver, BC, March 2008.

Gorman, Melanie. Dermal Exposure to Pesticides Among British Columbia (B.C.) Tree Planters. Presented at the 20th International Conference on Epidemiology in Occupational Health. San Jose, Costa Rica, June 2008.

Gorman, Melanie. Fertilizer Exposure and Respiratory and Dermal Health among British Columbia Tree Planters. Presented at the CARWH-RRSSTQ 2008 Occupational Health and Safety Conference. Montreal, QC, June 2008.

Gorman, Melanie. Fertilizer Exposure and Respiratory and Dermal Health among British Columbia Tree Planters. Presented at the 21st Annual UW/UBC/SFU Occupational and Environmental Health Conference. Blaine, WA, January 2009.

Gorman, Melanie. Exposure to Heavy Metals Among British Columbia (B.C.) Tree Planters. (2008) Presented to American Industrial Hygiene Conference and Exposition. Minneapolis, MN, June 2008.