Intact modern asphalt shingles are not toxic to touch or live under, but are asphalt shingles toxic to water? Partly. Across five runoff studies compiled by Degenhart and Helmreich (2022), median zinc in asphalt shingle roof runoff ranged from 2.5 to 1,000 µg/L, above Germany’s 60 µg/L groundwater threshold in three of the five, and copper-granule algae-resistant shingles were the second-largest roofing source of copper in Washington’s Puget Sound basin. Shingles made before the early 1980s are a separate issue: the Minnesota Department of Health lists asphalt roofing shingles and felt among products that contained asbestos. Because asphalt shingles top four out of five U.S. homes and more than 12.5 billion square feet are made each year, per the Asphalt Roofing Manufacturers Association (ARMA), their runoff is one of the most widespread diffuse pollution sources in the built environment.
By The Roofing Brief Team. Last reviewed: October 2026.
Are asphalt shingles toxic to people?
For a person living under or handling an intact modern shingle, the main hazards are asbestos in old roofs and dust or fumes during work, not the installed product. The Minnesota Department of Health says asbestos use in roofing declined rapidly after the early 1980s, that intact asbestos-containing asphalt roofing is “generally considered nonfriable and not hazardous,” and that breaking, sanding, cutting or sawing it can release fibers. If a roof predates the early 1980s and the material is unmarked, MDH advises assuming it contains asbestos or having a certified inspector sample it before tear-off.
What actually washes off an asphalt shingle roof?
Four pollutant streams leave an asphalt shingle roof during rain: eroded mineral granules and fine sediment; dissolved metals (zinc, copper and lead); polycyclic aromatic hydrocarbons (PAHs) from the asphalt; and polymer particles from SBS-modified lines such as Owens Corning Duration FLEX. Each starts in a different layer of the shingle and behaves differently once it reaches a gutter, a storm drain and a stream.
The U.S. EPA’s WARM documentation for asphalt shingles gives the composition by weight: asphalt cement 19 to 36 percent, a mineral stabilizer such as limestone or dolomite 8 to 40 percent, sand-sized mineral granules 20 to 38 percent, and an organic or fiberglass felt backing 2 to 15 percent. The granules shed as sediment, the asphalt can leach organic compounds, and the copper or zinc dosed into algae-resistant granules dissolves out over the roof’s life.
How polluted is asphalt shingle roof runoff?
It depends heavily on the study and the roof system. Degenhart and Helmreich’s review of 42 studies (Frontiers in Environmental Chemistry, August 2022) compiled median metal concentrations from asphalt shingle roof runoff in its Table 6 and compared them with Germany’s GFS groundwater insignificance thresholds: zinc 60 µg/L, lead 1.2 µg/L and copper 5.4 µg/L. The two older studies (1993 and 2004), which drained through galvanized gutters, sit far above those thresholds; the 2015 Washington panel tests sit below them for zinc and lead.
| Study (median values) | Zinc, µg/L | Lead, µg/L | Copper, µg/L | Zinc vs GFS 60 µg/L |
|---|---|---|---|---|
| Chang and Crowley (1993) | 1,000 | 43.0 | not reported | ~17x above |
| Chang et al. (2004) | 859 | 25.0 | 18.0 | ~14x above |
| Buffam et al. (2016) | 300 | not reported | not reported | 5x above |
| Winters et al. (2015), panel 1 | 7.00 | 0.06 | 30.0 | below |
| Winters et al. (2015), panel 2 | 2.50 | 0.07 | 2.10 | below |
| German GFS threshold | 60 | 1.2 | 5.4 | reference |
| U.S. EPA freshwater aquatic life criterion (hardness 100 mg/L) | 120 acute and chronic | 65 acute, 2.5 chronic | site-specific (Biotic Ligand Model) | reference |
Sources: Degenhart and Helmreich (2022), Table 6; EPA national recommended aquatic life criteria table. The review notes that elevated heavy metals appeared in runoff from most roof types “usually due to the used gutter materials,” so a 1,000 µg/L zinc reading reflects the whole roof system, not the shingle alone.
Where do the metals in shingle runoff come from?
The metals come from three places: biocidal granules dosed with copper or zinc to resist algae, the gutters and flashing that drain the roof, and dust settling from nearby traffic. A U.S. Geological Survey study by Van Metre and Mahler (Chemosphere, 2003) sampled particles washed from asphalt shingle and galvanized metal roofs 12 and 102 meters from a major Austin, Texas expressway. Zinc, lead, pyrene and chrysene in most samples exceeded sediment quality guidelines for probable toxicity to bottom-dwelling organisms; metal roofing was a source of cadmium and zinc, and asphalt shingles a source of lead. Rooftop washoff supplied an estimated 55 percent of the watershed zinc load, and the roofing materials themselves about 20 percent of the zinc and 18 percent of the lead.
Modern algae-resistant shingles add copper on purpose. McIntyre, Winters and colleagues at Washington State University tested 14 roofing materials over 4.5 years (Environmental Pollution, 2019). Copper from the copper-granule shingle panel was explained by rainfall amount, not panel age, so it kept leaching through the study, and the panel was projected to release 0.40 g of copper over 10 years versus under 0.01 g for the standard shingle. With asphalt shingles at about 71 percent of roof area in the Puget Sound basin, the authors estimated algae-resistant shingles supply 24.9 percent of roof-sourced copper, behind chromated copper arsenate treated wood shakes at 57.8 percent.
The same study found zinc from the algae-resistant shingle panel fell to background levels about 1.6 years after installation, while galvanized metal roofing (73.7 percent) and painted galvanized roofing (22.0 percent) dominated roof-sourced zinc. The copper and zinc that kill Gloeocapsa magma on the shingle leave in the first flush of each storm. Our guide to roof moss and algae killers covers the zinc and copper products involved, which are the same metals that show up downstream.
Is zinc runoff from galvanized steel harmful to aquatic life?
Yes, at high enough concentrations. Zinc washing off galvanized steel roofs, gutters and downspouts leaves mostly in dissolved form, more than 90 percent Zn2+ in several studies, the bioavailable form that harms aquatic life. The EPA’s recommended freshwater aquatic life criterion for zinc is 120 µg/L for both acute and chronic exposure at a water hardness of 100 mg/L, and the limit drops in softer water. The saltwater criteria are 90 µg/L acute and 81 µg/L chronic.
Those EPA figures are a U.S. surface water benchmark, so they are not the same yardstick as the German GFS groundwater threshold of 60 µg/L used in the table above. Each state sets the criteria that apply to a given stream under the Clean Water Act, so local limits may differ from the 120 µg/L national recommendation.
Galvanized steel is steel with a thin zinc coating, and rain dissolves that zinc as the coating corrodes. A review of copper and zinc roofing by Galster and Helmreich (2022, Water) found that zinc in metal roof runoff is mostly dissolved, with dissolved Zn2+ shares above 90% in several studies, and concluded that this runoff is harmful especially to aquatic life and needs treatment before discharge. The same review reports that new, uncoated galvanized roofs had higher zinc concentrations than older painted ones, and it describes Galfan (95 percent zinc, 5 percent aluminum) and Galvalume (55 percent aluminum, 45 percent zinc) coatings as ways to raise corrosion resistance.
This matters on a shingle roof too. A shingle roof drained by galvanized gutters and downspouts sends both zinc sources down the same pipe, and Degenhart and Helmreich traced elevated metals on most roof types to gutter materials. Aluminum or vinyl gutters, which carry no zinc coating, avoid that second zinc source.
Do asphalt shingles leach PAHs from the bitumen?
Yes, but at low levels in controlled tests. Bitumen is a petroleum residue that contains PAHs, and Shell researchers Brandt and de Groot leach-tested nine petroleum bitumens and one asphalt (Water Research, 2001). They found equilibrium PAH concentrations in the leach water stayed well below surface water limits in several EU countries and more than an order of magnitude below the then-current EU limits for drinking water, with equilibrium reached after 3 to 6 days of contact.
Particles are the bigger PAH pathway. The USGS Austin study found pyrene and chrysene, both PAHs, above sediment toxicity guidelines in particles washed from roofs 12 and 102 meters from an expressway, which mixes roof material with traffic fallout. The defensible reading is that shingle asphalt is a real but secondary PAH source, smaller in exceedance terms than the zinc and lead signal in the 1993 and 2004 studies.
Are asphalt shingles a microplastics source in stormwater?
Only some shingles contain polymers. SBS-modified lines are marketed that way: Owens Corning describes its Duration FLEX shingle, rated UL 2218 Class 4 for impact, as “made with a proprietary blend of SBS polymer modified asphalt” (Owens Corning, 2019). Those polymers could erode into runoff as the surface weathers and granules detach.
The direct evidence is thin. Published roadway and stormwater microplastic work mostly isolates tire and pavement wear, not shingle surfaces, and no published study we found gives a national mass estimate for shingle-derived microplastics. The Roofing Brief states that gap rather than filling it with a number.
How much sediment do America’s shingle roofs shed?
No measured national figure exists for granules washed into storm drains, but the mass on and off roofs is large. EPA’s WARM documentation estimates the U.S. manufactures and disposes of about 11 million tons of asphalt shingles a year (citing NERC, 2007), and granules are 20 to 38 percent of shingle weight, so roughly 2.2 to 4.2 million tons of mineral granules leave roofs in tear-off waste each year.
| Mass stream | Estimated annual U.S. mass | Basis |
|---|---|---|
| Asphalt shingle products manufactured | over 12.5 billion sq ft | ARMA |
| Asphalt shingles manufactured and disposed | ~11 million tons | EPA WARM, citing NERC (2007) |
| Mineral granules in that disposed tonnage | ~2.2 to 4.2 million tons | 11 million tons x 20 to 38 percent granule share (EPA WARM); our arithmetic |
| Asphalt cement in that disposed tonnage | ~2.1 to 4.0 million tons | 11 million tons x 19 to 36 percent (EPA WARM); our arithmetic |
| Granules washed to storm drains during service | not measured nationally | No published national estimate found |
Most granule mass stays embedded until tear-off and then goes to landfill or recycling; the fraction that erodes into gutters during the roof’s service life is the part that becomes a chronic sediment and metals load in urban waterways. An earlier version of this report gave a 100,000 to 300,000 ton national washoff estimate built on an assumed 2 to 5 percent washoff rate; it was removed in October 2026 because the rate is not measured.
What solvents damage asphalt shingles?
Strong hydrocarbon and chlorinated solvents dissolve asphalt, which is why the lab test for asphalt purity, ASTM D2042-22, measures solubility in trichloroethylene or toluene. On a roof, ARMA’s guidance on algae discoloration says stains may be lightened with a solution of household bleach (sodium hypochlorite) and water, that other cleaning chemicals or methods should not be used without the shingle manufacturer’s approval, and that the roof becomes slippery, so ARMA encourages hiring professionals.
What should I do about shingle runoff? Decision table
| If your situation is… | Do this | Source or threshold |
|---|---|---|
| Roof installed before the early 1980s, material unmarked | Assume asbestos or have a certified inspector sample it before cutting or tearing off | Minnesota Department of Health |
| Collecting rainwater for drinking or cooking | Do not use asphalt-roof water untreated; filter and lab-test for zinc, lead and copper first | Study medians up to 1,000 µg/L zinc and 43 µg/L lead (Degenhart and Helmreich, 2022) |
| Collecting rainwater for a garden | Use a first-flush diverter and keep it off edible leaves | Metals and particles peak early in a storm |
| Choosing a new shingle near a salmon stream or sensitive water | Weigh a non-algae-resistant shingle against algae staining | Copper-granule panel: 0.40 g Cu over 10 years vs under 0.01 g standard (McIntyre et al., 2019) |
| Galvanized gutters and downspouts | Replace with aluminum or vinyl at the next gutter job | Gutters drove elevated metals on most roof types (Degenhart and Helmreich, 2022) |
| Cleaning algae or moss | Use bleach and water per the shingle maker’s directions; no solvents | ARMA; asphalt dissolves in trichloroethylene and toluene (ASTM D2042) |
| Draining to a storm sewer in a soft-water area | Add a rain garden or bioretention cell at the downspout | EPA zinc criterion of 120 µg/L applies at hardness 100 mg/L and drops in softer water |
Methodology and limitations
The concentration data here are measured medians from peer-reviewed studies, cited inline to source and year, and shown study by study rather than as a single headline range. The mass estimates combine two EPA inputs (11 million tons disposed and the 19 to 38 percent component shares); the arithmetic is ours. For how shingles compare with every other material on U.S. homes, see our roofing material market share report.
Three limitations bound these numbers. First, runoff concentrations are site specific: rainfall pH, the preceding dry spell, roof age, gutter material and distance from traffic all change the result, which is why the five study medians span 2.5 to 1,000 µg/L zinc. Second, the German GFS thresholds are a groundwater reference; U.S. criteria differ by state and receiving water, so exceedance multiples show relative severity, not a regulatory violation. Third, the oldest high readings (1993 and 2004) came from roofs with galvanized gutters and rainwater already elevated by nearby industry, per the review, and may not represent a current shingle on aluminum gutters.
How can roof runoff pollution be reduced?
Runoff pollution from shingle roofs can be cut at the roof, the downspout and the ground. None make runoff drinkable without treatment.
- Choose lower-leaching surfaces where practical. In the WSU panel study, the standard shingle leached under 0.01 g of copper over a projected 10 years versus 0.40 g for the copper-granule shingle; weigh that against the algae resistance you give up.
- Intercept the first flush. A first-flush diverter sends the initial runoff of each storm, where metals and sediment peak, away from any collection tank.
- Add a green roof or bioretention. Rain gardens capture sediment and adsorb metals; see our green roof cost, types, and load guide.
- Be cautious with rain barrels. A gutter rain barrel suits garden water; with lead medians up to 43 µg/L, never drink it untreated.
For where the roughly 11 million tons of disposed shingles go, see our shingle waste and recycling report and 2026 roofing material carbon report.
Frequently asked questions
Are asphalt shingles toxic?
Not to touch or live under when intact and modern. The concerns are asbestos in roofs from before the early 1980s (Minnesota Department of Health) and runoff: five study medians put zinc in shingle runoff at 2.5 to 1,000 µg/L, above a 60 µg/L groundwater threshold in three of five (Degenhart and Helmreich, 2022).
Is rainwater from an asphalt shingle roof safe to drink?
Not without treatment. Published medians reach 1,000 µg/L zinc and 43 µg/L lead (Degenhart and Helmreich, 2022); filter and lab-test before potable use.
Do asphalt shingles pollute stormwater?
Yes. A USGS study (Van Metre and Mahler, 2003) found particles washed from roofs near an Austin expressway exceeded sediment quality guidelines for zinc, lead, pyrene and chrysene, with asphalt shingles a source of lead and rooftop washoff about 55 percent of the watershed zinc load.
What are the black or colored granules I find in my gutters?
They are the mineral granules that surface asphalt shingles, 20 to 38 percent of a shingle’s weight per EPA WARM data. Some loss is normal weathering; heavy accumulation can signal an aging or hail-damaged roof, and on algae-resistant shingles the granules carry copper or zinc that dissolves into runoff.
Do asphalt shingles contain microplastics?
Some do. SBS polymer-modified lines such as Owens Corning Duration FLEX contain polymers that could erode into runoff, but no published study we found gives a national mass estimate for shingle-derived microplastics, so the amount remains unquantified.
Why does my roof runoff contain so much zinc and copper?
Because algae-resistant shingles add them on purpose, and galvanized gutters add more zinc. In a 4.5-year Washington State University study (McIntyre et al., 2019), copper from a copper-granule shingle tracked rainfall rather than declining with age, and those shingles supplied an estimated 24.9 percent of roof-sourced copper in Puget Sound.