Lead, PCBs, mercury and other hazardous materials

Asbestos gets most of the attention, but the Norwood Block's hazardous materials report listed thirteen other materials, and several of them were more likely to hurt the demolition crew than the asbestos that had been carefully removed in sealed enclosures. Lead paint on the steel stairs could turn into toxic fume the moment someone touched it with a cutting torch. PCB caulking around the windows was a persistent environmental contaminant. Fluorescent tubes broken in a debris pile would release mercury vapour. The rooftop air conditioner held refrigerant that it is illegal to vent. The abandoned oil tank and the dry cleaner's floor drain raised the possibility of flammable vapours and contaminated soil.

This lesson covers these other hazardous materials: what they are, where they are found, how they harm workers and the environment, and how they are handled before and during demolition and renovation.

Lead

Lead was a common ingredient in paint until the second half of the twentieth century. It made paint durable and bright, and red lead primer was the standard rust protection for structural steel for decades. Lead was also used in plumbing solder, pipes, flashing, roofing, radiation shielding and some ceramic tiles.

Canada limited lead in consumer paints from the 1970s and tightened the limit over time; Health Canada advises that homes built before 1960 are likely to contain lead paint and those built between 1960 and 1990 may contain some. Industrial coatings on steel, such as red lead primer, stayed in use longer.

How lead harms workers

Lead enters the body mainly by breathing dust or fume, and by swallowing dust from hands, food, drinks or cigarettes handled with dirty hands. It builds up in the blood and bones. High exposure damages the nervous system, kidneys, blood and reproductive system, causing fatigue, headaches, stomach pain, memory problems, high blood pressure and reduced fertility. Lead also crosses the placenta and harms a developing baby. Workers can carry lead dust home on their clothes, boots and in their vehicles, exposing their children, who are especially vulnerable.

Which demolition tasks create lead exposure

Intact lead paint is not an inhalation hazard. Exposure comes from disturbing it:

• Torch cutting or welding painted steel, which vaporizes the lead into fume. This is the highest-exposure task in most demolitions and can produce extremely high airborne lead levels in seconds.
• Abrasive blasting and power grinding or sanding of lead paint.
• Manual demolition of painted walls and structures, which releases lead dust.
• Scraping, heat-gun stripping and dry sweeping of lead paint chips and dust.
• Cutting old lead pipe or soldered joints with heat.

In Manitoba, lead is controlled under Part 36 of the regulation, which requires the employer to assess the hazard, keep exposure below the ACGIH threshold limit value of 0.05 mg/m³ averaged over eight hours and as low as reasonably achievable, provide controls and protective equipment, and train workers. Many employers also follow published lead guidelines that set out procedures by task risk and recommend blood lead testing for workers with significant exposure.

Lead on the Norwood Block

Anika's specification avoided torch cutting of painted steel wherever possible. The steel stairs and the 1978 steel frame were taken down with a hydraulic shear on an excavator, which cuts steel cold without vaporizing the paint. Where torch cutting could not be avoided, such as freeing two embedded column bases, the paint was first stripped back at least 100 mm (4 in) on each side of the cut line with a chemical stripper, the cutter wore a powered air-purifying respirator with HEPA filters, and the area was cleaned with a HEPA vacuum afterward. Window frames with lead paint were removed as whole units. Workers washed hands and faces before eating, changed out of work clothes before leaving, and had no eating or drinking in the work area.

PCBs

Polychlorinated biphenyls (PCBs) are synthetic oils that were used from the 1930s to the late 1970s because they do not burn and do not conduct electricity. They were used in transformers, capacitors and fluorescent light ballasts, and as additives in caulking, sealants, paints and adhesives. PCBs persist in the environment for decades, build up in fish, animals and people, and are linked to cancer and effects on the immune, nervous and reproductive systems. Burning them can form even more toxic compounds.

• Light ballasts. Fluorescent fixtures installed before about 1980 often have ballasts with a small capacitor containing PCB oil. Ballasts marked "No PCBs" or made after 1979 generally do not. Ballasts are removed from the fixtures, checked, and those with PCBs or unknown status are packaged separately as PCB waste. Leaking ballasts are handled with chemical-resistant gloves and cleaned up as a spill.
• Caulking and sealants from the 1950s to the 1970s, especially around windows, expansion joints and masonry, can contain PCBs at high concentrations, and the PCBs can migrate into the adjacent brick or concrete.
• Transformers and capacitors in older electrical rooms may contain PCB oil. The utility or a qualified electrical contractor removes them.

PCBs are regulated federally under the federal PCB Regulations under the Canadian Environmental Protection Act, which set end-of-use deadlines for PCB equipment and require PCB wastes above set concentrations to be labelled, stored, transported and destroyed at approved facilities. Most of those deadlines have now passed, so any PCB ballast or equipment found during demolition has to be removed and managed as PCB waste, not left in place.

The Norwood Block's window caulking tested above the regulated level. Clearline Abatement Ltd. removed the windows as whole units and cut the caulking out, with the adjacent brick tested to see whether PCBs had migrated into it. They had not, beyond a thin edge that was removed with the caulking.

Mercury

Mercury is a liquid metal that gives off toxic vapour at room temperature. In buildings it is found in fluorescent tubes and compact fluorescent lamps, high-intensity discharge lamps, thermostats with glass switches, float switches in sumps and tanks, some old pressure gauges and manometers, and some old boilers and gas regulators. Breathing mercury vapour damages the nervous system and kidneys. Breaking a single fluorescent tube releases only a small amount, but breaking hundreds in a debris pile releases a lot, in a hot, enclosed space.

Lamps and mercury devices are removed intact before demolition, packed in their original boxes or in purpose-made containers, and recycled through a lamp and mercury recycler. On the Norwood Block, Dev Sandhu spent two days carefully removing 230 fluorescent tubes and packing them in boxes for the recycler, while an electrician removed the thermostats.

Refrigerants and ozone-depleting substances

Air conditioners, refrigerators, freezers, water coolers and chillers contain refrigerants, many of which deplete the ozone layer or are powerful greenhouse gases. Manitoba's rules on ozone-depleting substances and other halocarbons, and the federal Halocarbon Regulations for federal facilities, prohibit releasing them and require recovery by a certified technician before equipment is serviced, dismantled or scrapped. The rooftop unit on the Norwood Block was drained by a certified technician into a recovery cylinder and tagged as empty before the crane lifted it off.

Fuel tanks, pits and contaminated soil

Older buildings were often heated with fuel oil stored in tanks in the basement or buried in the yard. When the building switched to natural gas, the tank was often abandoned in place, sometimes with oil still in it. Old tanks, pits, sumps and drains can contain flammable liquids and vapours that ignite when hot work or a spark reaches them, and contaminated soil can expose excavation workers to chemicals.

Removing a fuel tank is specialist work. In Manitoba, tanks for petroleum products are covered by provincial rules on the storage and handling of petroleum products, which require removal by a qualified contractor and assessment of the soil around a tank when it comes out. On the Norwood Block, the tank contractor pumped out the remaining oil, tested the tank atmosphere, made it safe by purging and ventilation, cut it open only after a gas test showed no flammable vapour, and removed it. Anika sampled the soil around it.

The dry cleaner was more serious. Dry cleaners commonly used tetrachloroethylene, a chlorinated solvent also called perchloroethylene or perc, which is toxic and a probable human carcinogen. Spills and leaks soaked into floor slabs and the soil below and can give off vapour for decades. Anika's drilling found solvent in the soil under the floor drain. The slab and soil in that area were treated as contaminated: workers breaking the slab wore respirators with organic vapour cartridges and chemical-resistant gloves, air was monitored with a photoionization detector, and the contaminated soil was excavated and taken to a facility licensed to receive it, under Manitoba Environment and Climate Change requirements.

Other hazards worth a line in the plan

• Radioactive sources in some old ionization smoke detectors and self-luminous exit signs, which are collected and returned rather than crushed.
• Treated wood with creosote or other preservatives, which should not be burned.
• Bird, bat and rodent droppings in attics, towers and vacant spaces, which can carry fungal and viral diseases and are wetted and removed with respiratory protection.
• Sharps and discarded needles in buildings that have been vacant, which call for puncture-resistant gloves, a sharps container and caution when reaching into hidden spaces.
• Chemicals left behind by former tenants, in drums, pails and laboratories.

A lead exposure check

Owen uses a short program to compare the lead results from two tasks with the limit and decide what controls are needed.

# Lead exposure assessment for two tasks (invented results, ug/m3).
LIMIT_TLV = 50   # 0.05 mg/m3 ACGIH TLV, as ug/m3
LIMIT_US = 50    # US permissible limit
ACTION_US = 30   # US action level

tasks = {
    "shearing painted steel stairs": [(180, 12), (60, 4)],     # (minutes, ug/m3)
    "torch cutting with paint stripped": [(45, 140), (15, 30)],
}
for task, parts in tasks.items():
    twa = sum(m * c for m, c in parts) / 480
    print(f"{task}: 8-hour TWA {twa:.1f} ug/m3")
    if twa > LIMIT_US:
        print("   above the limit: engineering controls, respirators, hygiene, medical surveillance")
    elif twa > ACTION_US:
        print("   above the US action level: monitoring and blood lead testing")
    else:
        print("   below the action level: keep current controls")

shearing painted steel stairs: 8-hour TWA 5.0 ug/m3
   below the action level: keep current controls
torch cutting with paint stripped: 8-hour TWA 14.1 ug/m3
   below the action level: keep current controls

Even with the paint stripped back, the brief torch cut produces a high short-term concentration. Averaged over the shift it sits just under the action level, but the peak is why the cutter needs a respirator during the cut. Shearing the stairs cold keeps exposure low all day.