Everything you always wanted to know about chalk but were afraid to ask

Photo par frank mckenna sur Unsplash

In the mid-fifties, climbing chalk was brought to the climbing world by John Gill, a former gymnast. (1) Nowadays, more than thirty local or international compagnies are selling climbing chalk, wether liquid or solid, in chunk or powder version.(2) Magnesium carbonate is part of a climber's attire and considered as an essential item to any vertical endeavour. On a buzy night at the gym or during a climbing competition, its white dust cloud becomes clearly visible. Climbers and gym employees are inevitably exposed to magnesium carbonate dust particles. Looking at the scientific litterature, exposition to elevated concentration of magnesia dust could be linked with symptoms such as headaches, coughing, respiratory tract or occular irritation.(3) However, no quantitative data is available.

The Climbers' Clinic will try to answer a burning yet taboo question: are there any health related risks linked to an exposition to magnesium carbonate? We will look at the substance toxicity, the size of its particles, the concentrations reached in climbing gyms and how they compared to ambiant and occupational air standards.

Magnesium Carbonate Toxicity

Climbing chalk, magnesia alba or magnesium carbonate (MgCO³) is a salt derived from magnesite, a mineral. (4) Its drying properties are well know and when climbers use it on their hands, solid particles are relased in the ambiant air. Is the substance toxic? According to safety labels used in the chemical industry, magnesium carbonate is graded 1 (out of a 4 points scale) for health hazards. Exposure can cause irritation to the respiratory tract with only minor residual injury. (5)(6)(7)

Magnesium carbonate Material Safety Data Sheet, Spectrum Chemicals 2012. 
Technically speaking, its is hydrated magnesium carbonate hydroxide that is found in suspension in the air. Similar molecule, with a thin water film around it. 

Despite a low toxicity, every industrial safety notice states that magnesisum carbonate can cause respiratory tract irritation, coughing and breathing difficulties. Direct contact can also cause irritation or redness. Uppon inhalation, moving to fresh air is advised and rinsing the hands or eyes for 15 minutes is recommended after any contact with the substance. Definitely the industry has much higher safety precautions than the climbing world! Still, even if it is safe for our use, deposition of solid particules of magnesia can produce a mechanical irritation of the muquous layer in the respiratory tract.(8) 

Size of magnesia particles

In order to understand how dust particles can affect our respiratory system, we have to look at their size and the depth of their penetration in the breathing apparatus (see image below). Dust particles are measured in micrometers or microns (µm). As a comparison, a human hair has a diameter of 50 microns but ultrafine particles measure less than 1 micron. (35)

https://www.ccohs.ca/oshanswers/chemicals/how_do.html

Looking at particle size, total dust can be divided in three different fractions, summarized in the table below. (9)(11)

The 10 microns size was established by international agencies as the boudary for respirable particles, since particles this diameter and lower can settle in the lungs. (12) Three measures monitor their level: PM10, PM2.5 and PM1. They are the Particulate Matter Concentration (in mg per m³ or µg per m³) up to the number size in microns. For instance PM 2.5 refer to the concentration of particles up to 2.5 microns.

Now, let's look at the size of airborne particles found in climbing gyms. (3)(8) According to the only two studies published on the topic, it ranges from 0.7 to 10 microns, as illustrated from the graph below. In addition, studies that analyzed the indoor air of gymnastics facilities (that also use magnesia) concluded that 90% of dust particle diameter size was higher than 1 micron and averaged 2.6 µm. Moreover, utilisation of magnesia was increasing the concentration of particles between 0.4 to 10 microns compared to situations where it was not used. (13)(14)

Magnesium carbonate dust particles are thus small enough to reach as deep as the alveoli in the respiratory system. When measuring fractions of magnesia dust, Castro et al (2015) and Alves et al (2016) found that

• inhalable fraction was 80% of total dust
• thoracic fraction was 54% of total dust
• respirable fraction was 10-14% of total dust 

Given those numbers, are there any "safe" concentrations to magnesium carbonate particles? 

Occupational tresholds and ambiant air standards.

Many governmental body have establised treshold levels for dust exposure. The Permissible Exposure Limit or the Treshold Limit Value respectively represents "acceptable" dust particule exposition in absolute or measured in time and the level at which a worker can be exposed daily wihtout longterm adverse effects. (15)(16) 

The OSHA (Occupational Safety and Health Administration), the ACGIH (American Conference of Governmental Industrial Hygienists), the NIOSH (National Institute for Occupational Safety and Health) have all estalished dust exposition standards in the workplace. 

The CCOHS (Canadian Center for Occupational Health and Safety) and most provincial health and safety agency use the american standards for their own occupational exposure limits. This includes WorkSafe BC, Alberta Occupational Health and Safety, the CNESST (Commission des normes de l'équité de la santé et de la sécurité au travail, in Quebec) and Ontario Health & Safety. We did not checked the other provincial and territorial agencies. The current standards are summarized below: (5)(17)(18)(19)(20)(21)

_{However, most of the previous values were developped for industrial work places where hazardous materials pose potiential health risks. Such occupational exposure limits may not be applicable to indoor air quality in schools, gymnasium or offices.(22)  Yet, in North America, no norms exist for indoor air quality, although standards do exist for ventilation and specific contaminants such as mold or carbon monoxide.(23) No standard for dust or magnesia dust was found. Thus, the only other guidelines we can refer to for climbing gyms are ambiant (or outdoor) air quality standards.}

_{The WHO (World Health Organization), the EPA (Environmental Protection Agency in the USA), the  CCME (Canadian Counsil of Ministers of the Environment)  and the various provincial agencies have established the following standards for ambiant air, summarized in the table below. (24)(25)(26)(27()(28)(29)(30)(31) You will note concentrations are now expressed in µg: 1000µg equals 1mg.}

  

_{*Québec: Ministère du developpement durable, de l’environnement et de la lutte contre les changements climatiques}  **OMECC: Ontario Ministry of the Environment and Climate Change

Magnesium Carbonate Dust Concentrations in Climbing Gyms

_{Amongst the scientific litterature, only 4 articles measured dust concentration in indoor climbing gyms.(3)(32)(33)(8) Here are their results, summarized in the table below.}

According to the previous results, we can state that even if magnesia dust concentrations are lower than occupational norms, they largely surpass ambiant air quality tresholds for both PM10 and PM 2.5. Even the sampling done during low occupancy times (minimum colomn) are above the recommended level. Are there any health effects of such conditions?

Respiratory system health effects

_{According to Moshammer et al. it is the peak exposure that will determine respiratory tract effects more than the cumulative burden on the pulmonary system.(8) In their study, the authors examined short term effect of a single exposition to climbing chalk. Higher was the exposure (in either the duration of the climbing session or the level of magnesia dust concentration), greater was the decrease in pulmonary expiratory capacity. A two-fold physiological reaction was observed. Firstival, high magnesia dust concentration resulted in a reflex contraction of smooth muscles around the bronchioles. This increases the resistance of larger airways. The body then secretes nitric oxide to relax those muscles. Following this chemical stress, the second inflammatory reaction is triggered by the body's immune system, as observed in the epithelium muquous layer. This reaction can be observed up to 24 hours after the initial exposition and affects smaller diameter airways.}

Inflammatory reaction in a bronchiole
https://canadiem.org/approach-asthma-ed/

_{Although the authors' results were not statistically significant, a reduction in pulmonary function was measured directly after a climbing session. This effect was greater in people already presenting a respiratory fragility. Moreover, after 3 hours of participation in a climbing competition, a greater reduction was observed in competitors having started earlier or amongst young climbers. The 24h reaction was observed in people already presenting an hyperreactivity of the pulmonary system.} 

_{We still don't know if repeated exposure has repercussion on a person's health and if those aforementionned effects are reversible. A larger study is necessary.}

_{In sum:}

• _{Magnesium carbonate has a low toxicity}
• _{Use of climbing chalk mainly produces dust particles higher than 1 micron and up to 10 microns. It is not a significant source of ultrafine particles}
• _{Health hazards depends on the size of particles and where they deposit along the repiratory system. (9) (10)} 
• _{A great majority of of airborne magnesia particles is intercepted by the nose, mouth, trachea, bronchi and bronchioles. However, 10-14% of particles are small enough to deposit in the alveoli.} 
• _{Even if climbing gym dust particle concentrations are lower than occupational norms, they are always above ambiant air standards for both PM 10 and PM 2.5}
• _{People with hyperreactive airways are more susceptible to be affected by poor air quality. Climbers with respiratory conditions should follow their Doctor's recommendations if their symptoms were to be exacerbated following an indoor climbing session.}

Considering the growing number of kids starting indoor rock climbing and according to Health Canada: concentrations of PM 2.5 should be maintained to a minimum, since their is no safe treshold below which no health effect are observed. (34) The WHO also states that we should strive to atteint the lowest concentrations possible, taking into account local constraints and public health priorities. (24)The Climber's Clinic is preparing another article on how to improve air quality in climbing gyms. Stay tuned!

Special thanks to Marie-Pier Breault from MDDLECC and Patrick Hughes from CCHST for their precious informations, Thibault Stimpling for scientific articles and  Milan Brlek for finding typos.


References

(1) John Gill https://en.wikipedia.org/wiki/John_Gill_(climber)

(2) A search performed in November 2019 (on  epictv, amazon, verticall, Mec, Lacordée, Au vieux Campeur, Bachlii sport, REI, EMS, Climb On) identified  the following brands of chalk sold for climbing purposes: 8Bplus, 8C+, Beal, Black Diamond, Bleausard, Bison Design, Camp, Carbon Grip, Chalk Carter, Chalk Factory, DMM, Easy Grip, EB, Edelrid, Fixe, Flashed, Friction Labs, I'bbz, Joshua Tree, MadRock, Mammut, Massif, Matawi, Metolius, Midas, Myélore, Ocun, Petzl, Primo, Psychi, Rock Technologie, Roze, Salty Lance, Sattva, Simons, Snap, So Ill, Stubai, Tembo, Trango, Wild Country and Yama Tech Climbing.

(3) Weinbruch S. et al (2008) Dust exposure in indoor climbing gyms. Journal of Environmental Monitoring. 10, 648-654.

(4)Magnesium Carbonate   https://en.wikipedia.org/wiki/Magnesium_carbonate

(5) Environmental Health & Safety(2004) Magnesium Carbonate Hazard/Safety Labels for Chemical Containers  www.psh.ca/MSDS/Magnesium%20Carbonate%20-%20A&K%20Petrochem.htm

(6) Spectrum Chemicals (2012) Magnesium Carbonate Hydroxide pentahydrate Material Safety Data Sheet https://www.spectrumchemical.com/MSDS/M0057.pdf

(7) Fisher Sci (2014) Magnesium Carbonate Material Saftery Data Sheet, https://beta-static.fishersci.com/content/dam/fishersci/en_US/documents/programs/education/regulatory-documents/sds/chemicals/chemicals-m/S25400.pdf

(8)Moshammer (2016) Lung function and dust in climbing halls. Rev Environ Health.31(4):401-407.

(9) World Health Organization (1999) Hazard Prevention and Control in the Work Environment: Airborne Dust. https://www.who.int/occupational_health/publications/en/oehairbornedust.pdf

(10) Particulates https://en.wikipedia.org/wiki/Particulates

(11) Canadian Center for Occupational Health (2018) How to particulates enter the respiratory system?  https://www.ccohs.ca/oshanswers/chemicals/how_do.html

(12) Particulate Matter Basis (n.a) Environmental Protection Agency,  https://www.epa.gov/pm-pollution/particulate-matter-pm-basics

(13) Castro, A. et al. (2015) Indoor aerosol size distributions in a gymnasium. Science of the total environment 524-525, 178-186.

(14) Alves C. et al (2014) Particulate matter in the indoor and outdoor air of a gymnasium and a fronton. Environ Sci Pollut Res 21 (21) 12390-402.

(15)Treshold limit value (n.a) https://en.wikipedia.org/wiki/Threshold_limit_value

(16) Permissible exposure value (n.a.) https://en.wikipedia.org/wiki/Permissible_exposure_limit

(17) National Institute for Occupational Safety and Health (2019) Pocket Guide to Chemical Hazards, Magnesite, https://www.cdc.gov/niosh/npg/npgd0373.html

(18) CCOHS (2017) Occupational Hygiene - Occupational Exposure imits
https://www.ccohs.ca/oshanswers/hsprograms/occ_hygiene/occ_exposure_limits.html

(19)Québec (2019) Règlement sur la santé et la sécurité du travail, Loi sur la santé et la sécurité du travail http://legisquebec.gouv.qc.ca/fr/pdf/cr/S-2.1,%20R.%2013.pdf

(20) https://www.worksafebc.com/en/law-policy/occupational-health-safety/searchable-ohs-regulation/ohs-guidelines/guidelines-part-05

(21) Ontario (2010) Occupational Health and Safety Act, Control of exposure to biological or chemical agents  https://www.ontario.ca/laws/regulation/r10419

(22) CCOHS (2020) Indoor Air Quality https://www.ccohs.ca/oshanswers/chemicals/iaq_intro.html

(23)Occupational Safety and Health Administration (n.a) Indoor Air quality
 https://www.osha.gov/SLTC/indoorairquality/index.html

(24) World Health Organization (2005) WHO Air quality guidelines for particulate matter, ozone, nitrogen dioxide and sulfur dioxide Global update 2005 Summary of risk assessment.
https://apps.who.int/iris/bitstream/handle/10665/69477/WHO_SDE_PHE_OEH_06.02_eng.pdf?sequence=1&isAllowed=y

(25)United States Environmental Protection Agency(2014) Typical Indoor Air Pollutants https://www.epa.gov/sites/production/files/2014-08/documents/refguide_appendix_e.pdf

(26) United States Environmental Protection Agency(2016) Integrated Review Plan for the National
Ambient Air Quality Standards for Particulate Matter.
https://www3.epa.gov/ttn/naaqs/standards/pm/data/201612-final-integrated-review-plan.pdf

(27)CCME (2015) Canadian Ambient Air Quality Standards (CAAQS) for Fine Particulate Matter (PM2.5) and ozone
 https://www.ccme.ca/files/current_priorities/aqms_elements/caaqs_and_azmf.pdf    et
http://airquality-qualitedelair.ccme.ca/

(28) Ministère du developpement durable, de l’environnement et de la lutte contre les changements climatiques (2016) Normes et critères québécois de qualité de l'atmosphère Version 6
http://www.environnement.gouv.qc.ca/air/criteres/index.htm

(29) Carex Canada (n.a) Outdoor Air Pollution Profile
https://www.carexcanada.ca/profile/outdoor_air_pollution/

(30) BC Air Quality Objectives & Standards (2020)
https://www2.gov.bc.ca/gov/content/environment/air-land-water/air/air-quality-management/regulatory-framework/objectives-standards

(31) Alberta Government (2019)Alberta ambient air quality objectives and guidelines summary https://open.alberta.ca/publications/9781460134856

(32)Weinbruch, S. et al. (2012) Reducing Dust exposure in indoor climbing halls. Journal of Environmental Monitoring. 14, 2114-2120.

(33)Almand-Hunter, B.B. (2013) Dust exposure in indoor climbing facilities, Department of Mechanical Engineering, University of Colorado, Boulder, CO

(34) Health Canada (2012) Guidance for fine particulate matter (PM2.5) in residential indoor air   https://www.canada.ca/en/health-canada/services/publications/healthy-living/guidance-fine-particulate-matter-pm2-5-residential-indoor-air.html

(35) Micrometer https://en.wikipedia.org/wiki/Micrometre