Hazard Analysis — Construction dust


Problem:

Workers who cut bricks, blocks, stone, concrete, tile or terrazzo may be exposed to construction dust.


Risk Description:

Chronic obstructive pulmonary disease (COPD) includes chronic bronchitis and emphysema. Chronic bronchitis is present when someone has a regular cough with phlegm for at least 3 months per year for two years.  Emphysema is present when there is destruction of the walls of the airspaces of the lung.  The destruction of airspaces means there is less lung surface; loss of lung surface reduced the ability of the lung to transfer oxygen into the blood stream.

Smoking is the primary cause of COPD, but smoking alone does not explain all COPD, as only 15-20% of smokers developed COPD and 10% of deaths from COPD occur in persons who never smoked. Occupational exposures to dusts and chemicals (vapors, irritants, fumes) also cause COPD; the specific exposures in construction linked to COPD are wood dusts, cadmium, silica, welding fumes, cement dust, asbestos, and possibly isocyanates.  For someone with heavy dust exposure over many years, the dust contributes as much to COPD as smoking does.  Across all occupations, about 15% of COPD is caused by occupational exposures. 

The U.S. National Health Interview Survey for the years 1988-1994 reported that workers in construction trades had more COPD than other workers; in this survey 13.4% of white men in construction had COPD. A study of sheet metal workers followed over a 10-year period found they lost more lung function if they were exposed to asbestos and also smoked.

Airflow in nonsmokers without respiratory disease declines by 25 to 30 ml per year beginning at about age 35.The rate of decline of airflow is faster for smokers than for nonsmokers, and faster for those exposed to lots of dust. Individuals with COPD have more frequent chest illnesses, which also decrease lung function for several months.

Treatment of COPD focuses on smoking cessation and exposure reduction, medication to increase airflow and decrease phlegm production, and treatment of intermittent chest infections.Someone with COPD needs a vaccination for pneumococcal pneumonia every 5 years, and annual influenza vaccination.  A small amount of lung function is regained when someone quits smoking, and the lung function decline slows to about the rate seen in never-smokers of the same age.


Level of Risk:

Exposures are of such a magnitude and character that a significant number of workers risk developing serious long or short term health effects.

In 1999 COPD ranked as the fourth leading cause of death with over 124,000 deaths, and was a primary or contributing cause of death for an estimated 8.5% of the U.S. population.  An estimated 16 million individuals in the U.S. had a diagnosis of COPD in 1994. Worldwide, COPD is projected to be the third leading cause of death by 2020.  80 to 90% of COPD is caused, at least in part, by tobacco smoking, but exposure to dust is an important risk as well.  The American Thoracic Society concluded that 15% of COPD was caused by occupational exposures, and that occupational dust and fume exposures can cause clinical bronchitis and loss of lung function in both smokers and nonsmokers.

Most construction workers are at risk of COPD; studies find an elevated prevalence of COPD across many trades, and most trades have tasks that create dust or fumes.  Many construction tasks have exposures to levels of dust which exceed the OSHA permissible exposure limit of 5 mg/m3 for non-specific dust.  Because many construction trades work alongside each other, a construction worker can be over-exposed to dust generated by a co-worker doing a different task.

Some experts have suggested that dust at construction sites is best described as quartz (silica) containing mixed dust, and quartz is clearly one component of dust related to lung injury.  The proportion of quartz in the overall dust exposure of any individual will vary by task, materials, specific years worked, work location, and likely other factors as well.  Tuckpointing had respirable dust levels as high as 8 mg/m3 as an 8 hour TWA, with quartz levels as high as 1.7 mg/m3 as an 8 hour TWA. In one study that looked at both exposure and disease, workers with higher cumulative dust exposures were more likely to have a chest x-ray showing mixed dust pneumoconiosis (lung scarring due to an exposure to mixed dust).  The prevalence of mixed dust pneumoconiosis was significantly increased after 25 years work at a tuckpointer or 33 years work as a concrete driller or grinder. 

Studies of miners have shown that long term exposure to dust at levels of 2 mg/m3 causes COPD, and that as the silica content of the dust increases the total exposure needed to cause disease decreases.  However, other dusts and fumes, including asbestos, cadmium and welding fumes also cause COPD, so silica is only one of the injurious components of construction dust.


Assessment Info:

You must determine whether exposures at your jobs exceed allowable limits for overall dust and specific dusts.

Silica is an important component of many construction dust exposures., and the PEL for silica exposure in construction is much lower than the PEL for non-silica containing dust, so it is essential to determine the silica content of any dust exposures.  OSHA has an e-tools site for silica that walks you through the process of assessment of silica exposure.

Exposure assessment must be done by a qualified person.  You may be able to to obtain assistance in measuring exposures from your State OSHA consultation service or from your contractor association. 


Regulations & Standards:

OSHA standard 1926.55, titled Gases, vapors, fumes, dusts, and mists, in safety and health regulations for construction must be in place. Exposure of employees to inhalation, ingestion, skin absorption, or contact with any material or substance at a concentration above those specified in the "Threshold Limit Values of Airborne Contaminants for 1970" of the American Conference of Governmental Industrial Hygienists, shall be avoided.

The current OSHA standard for overall dust which contain < 1% silica is 15 mg/m3.   The NIOSH recommended exposure limit for crystalline silica is 0.05 mg/m3.  NIOSH research shows that controlling exposures below this concentration should prevent all workers from obtaining silicosis.  American Conference of Governmental Industrial Hygienists (ACGIH) recommends a time weighted average exposures of less than 10 mg/m3 for total dust.  For respirable dust the ACGIH recommends a limit of 3 mg/m3 compared to an OSHA PEL for general industry of 5 mg/m3.

Federal OSHA Standards are enforced by the U.S. Department of Labor in 26 states. There are currently 22 states and jurisdictions operating complete State plans (covering both the private sector and state and local government employees) and 5 - Connecticut, Illinois, New Jersey, New York and the Virgin Islands - which cover public employees only. If you are working in one of those states or jurisdictions you should ensure that you are complying with their requirements.


Other Considerations:

Controlling worker exposure to dust also results in reductions in housekeeping or cleanup, reduced environmental contamination, and reduction in nuisance dust exposurers to the general public. Many cities and local governments have nuisance ordinances that may require dust controls.