How to read a toxicology report

Written by Tara Haelle (opens in a new tab)

Medically reviewed by Ecler Ercole Jaqua, MD, MBA, DABOM (opens in a new tab)

Knowing how to read a toxicology report — multiply parts per billion by the serving size in grams, and divide by 1,000 to find micrograms per serving — is one of the most empowering skills you can develop as a health-conscious consumer. If you've been following our Toxicology in Context series, you already understand that <a href="https://science.drinklmnt.com/did-you-know/toxins-vs-toxicology-why-dose-matters" rel="noopener noreferrer" target="_blank">detection doesn't equal danger</a>. Dose is what matters.If "any amount" of a heavy metal was dangerous for you, you couldn't eat carrots, spinach, apples, or seaweed — since all plants naturally absorb trace elements from soil and water. The issue isn't whether you can detect a metal in your food but whether there's enough of it to affect your health.So how do you figure that out? By doing the math.What if you could look at any lab report and understand — mathematically and contextually — what it means for your health? Not guess, not worry — actually know.The math is simpler than you think, and once you see how to convert parts per billion into real serving sizes, those big numbers will start making a lot more sense.Let's walk through it together.<h2>What Does Parts Per Billion Mean?</h2>Parts per billion (ppb) is a measurement of concentration. It’s a way to describe how much of one thing is present in a larger amount. In solid foods, ppb is the number of micrograms per kilogram. (Don’t worry, we’ll break this down further.)The number itself — billion — carries psychological weight. Our brains evolved to assess threats in our immediate environment, not to intuitively or automatically grasp quantities at this kind of scale.So what does one part per billion represent? <ul><li>Picture a 10-mile stretch of beach. One ppb is a single grain of sand on that entire beach. </li><li>Or consider an Olympic-sized swimming pool. One ppb is equivalent to a single drop of water in that pool.</li></ul>A single ppb is incredibly small. When a headline or report states "27 parts per billion of lead," that means 27 micrograms of lead in every kilogram (2.2 pounds) of food. Picture those 27 grains of sand distributed throughout 2.2 pounds. That's the concentration we're talking about.Following so far? Let’s double tap on defining a kilogram.A kilogram (2.2 pounds) is about the weight of a medium-sized pineapple — far more than you'd usually eat in a single serving. So that 27 ppb measurement isn’t what’s found in your drink or on your plate; it represents what you’d consume if you ate 8-10 servings of most foods.Lab reports list concentrations per kilogram for scientific accuracy, but news stories rarely translate that into actual serving sizes. The typical person doesn't convert kilogram measurements to actual serving sizes but you can once you know how.Let’s put those conversions into action with some real world examples.<h2>How to Convert ppb to a Serving Sizes (in 3 Steps)</h2>There’s a simple 3-step formula to convert ppb into the actual amount in a single serving:1. Find the ppb number2. Multiply it by the serving size in grams3. Divide by 1,000 to find out the micrograms per servingThat’s it. Now you know what’s in a portion.For example, Girl Scout cookies <a href="https://www.theguardian.com/us-news/2025/apr/05/girl-scout-cookies-heavy-metals-lawsuit" rel="noopener noreferrer" target="_blank">made headlines</a> not long ago over claims about heavy metals — lead, arsenic, cadmium, aluminum and mercury. The claims originated from a <a href="https://gmoscience.org/2024/12/27/danger-in-the-dough/" rel="noopener noreferrer" target="_blank">report</a> on a website that promises to reveal the “hidden dangers” in our food.The report labeled Peanut Butter Patties as one of the “most contaminated” cookies, citing 42.5 ppb of lead. That sounds like a lot, but that’s per kilogram (2.2 pounds) and there isn’t even a full kilogram in one box.Let’s calculate what is in a single serving of Peanut Butter Patties:Step 1: Find the parts per billion number. The amount given in the report is 42.5 ppb.Step 2: Multiply the ppb number by the serving size in grams. The nutrition label shows a serving is two cookies (25 grams).So 42.5 x 25 = 1,062.5Step 3: Divide by 1,000 to get micrograms per serving1,062.5 ÷ 1,000 = 1.06 micrograms per serving. Now remember how infinitesimal one microgram is — comparable to a grain of sand on a 10-mile stretch of beach. That’s roughly what you’d consume (<a href="https://science.drinklmnt.com/did-you-know/does-body-absorb-heavy-metals-bioavailability-explained" rel="noopener noreferrer" target="_blank">not absorb</a>) if you ate two Peanut Butter Patties. Next step: Let’s compare this to what’s naturally present in other foods.<h2>How Much Lead Is Natural in Vegetables?</h2>A <a href="https://www.sciencedirect.com/science/article/abs/pii/S0269749118322401" rel="noopener noreferrer" target="_blank">2018 peer-reviewed study</a> measured heavy metal levels in the five most consumed vegetables in the U.S: potatoes, carrots, onions, lettuce, and tomatoes. The researchers collected both organic and conventional samples of each one from four grocery stores in a Florida college town.Next, they tested the samples for nine metals: arsenic, cadmium, lead, chromium, barium, cobalt, nickel, copper, and zinc. To keep things simple, we’re just going to focus on what they found for lead since that’s what we looked at in the Peanut Butter Patties. Here are the results for average ppb of lead in the five vegetables Americans eat the most:

Vegetable	Organic (mcg/kg)	Conventional (mcg/kg)	Amount per standard serving
Tomato	5.0	7.7	~1 mcg per 1 medium tomato
Lettuce	12.0	25.3	~0.9 mcg per 1 cup of chopped lettuce
Onion	3.0	19.0	~3 mcg per 1 small onion
Carrot	7.2	22.4	~2.9 mcg per 1 medium carrot
Potato	32.6	16.5	~6 mcg per 1 medium baked potato

Let’s walk through our calculation steps again — this time, for organic potatoes.Step 1: Find the parts per billion number for organic potatoes. It’s 32.6. Step 2: Multiply it by the serving size in grams. The <a href="https://www.fda.gov/media/76882/download" rel="noopener noreferrer" target="_blank">FDA considers one serving</a> to be one medium-sized potato, which is about 148 grams. So 32.6 x 148 = 4,824.8.Step 3: Divide by 1,000 to find out the micrograms per serving.4,824.8 ÷ 1,000 = 4.82 micrograms per serving. That’s almost five times as much lead as there was in one serving of Peanut Butter Patties! And that’s for an organic potato too. The lead amounts in the other vegetables were higher in the conventional samples than in the organic ones, but it’s interesting that it happens to be higher in organic potatoes than in conventional potatoes. What about the other vegetables? We did the math for you, using those <a href="https://www.fda.gov/media/76882/download" rel="noopener noreferrer" target="_blank">FDA serving sizes</a>, so you can see how much lead is in other common organic vegetables:

Organic Vegetables	PPB (mcg/kg)	Standard serving size	Amount per standard serving
Tomato	5.0	148 g	0.74 mcg
Lettuce	12.0	85 g	1.02 mcg
Onion	3.0	148 g	0.44 mcg
Carrot	7.2	78 g	0.56 mcg
Potato	32.6	148 g	4.82 mcg

And here are the calculations for conventional samples of the same vegetables.

Conventional Vegetables	PPB (mcg/kg)	Standard serving size	Amount per standard serving
Tomato	7.7	148 g	1.14 mcg
Lettuce	25.3	85 g	2.15 mcg
Onion	19.0	148 g	2.81 mcg
Carrot	22.4	78 g	1.75 mcg
Potato	16.5	148 g	2.44 mcg

Even the highest levels here would require someone to eat multiple large servings at once to come close to the safety thresholds set by international health organizations. These trace amounts are exactly what scientists expect to find in food grown in soil.The bottom line: The amount of heavy metals in these vegetables is not a health risk. <h2>How Much Lead Is in LMNT?</h2>Now that you know what’s typical in food, let’s look at how much lead is in LMNT. An influencer tested LMNT for lead and found that it contained 27 ppb — results that align with our own testing. (We test every batch of our product for heavy metals as part of our <a href="https://science.drinklmnt.com/quality-testing/" rel="noopener noreferrer" target="_blank">quality control</a>.)But here's where that number often gets misread: a graphic from that report was presented in a way that made it appear as if a single serving contained 27 ppb of lead. It doesn't. 27 ppb is a concentration, not a per-serving dose. Here's how to translate it:Step 1: Find the parts per billion number. The amount is 27 ppb.Step 2: Multiply the ppb number by the serving size in grams. One stick pack is 3.5 grams.So 27 x 3.5 = 94.5Step 3: Divide by 1,000 to find out the micrograms per serving.94.5 ÷ 1,000 = 0.094 micrograms per serving. To put that in perspective: a single serving of the vegetables above contains 5 to 51 times more lead than an LMNT stick pack. And a stick pack itself sits more than five times below California's Prop 65 threshold — already one of the strictest limits.If the trace amount of metals in LMNT were dangerous, then eating vegetables would be far, far more dangerous. Instead, we know that vegetables are vital to a healthy diet — as are sodium and other electrolytes.<h2>Why Your Body Doesn’t Absorb Every Trace Metal You Eat</h2>Your body is smarter than you think. <a href="https://science.drinklmnt.com/did-you-know/does-body-absorb-heavy-metals-bioavailability-explained" rel="noopener noreferrer" target="_blank">It doesn’t absorb everything you eat</a>. Lots of factors affect how much of something you consume gets absorbed by your body. This is called bioavailability, and it includes: <ul><li>What other foods you eat with it — getting enough calcium, vitamin C, iron and other nutrients in healthy foods reduces the likelihood of absorbing lead</li><li>How the food is prepared</li><li>Your body’s natural protective systems</li><li>The form the metal is in</li></ul>Want to understand how this works? Read our next article “<a href="https://science.drinklmnt.com/did-you-know/does-body-absorb-heavy-metals-bioavailability-explained" rel="noopener noreferrer" target="_blank">Bioavailability explained: What your body absorbs</a>” to see why consumption doesn't equal absorption.  This was the fourth article in our six-part "Toxicology in Context: Heavy Metals" series. Want to read the other articles? Check them out below: <ul><li><a href="https://science.drinklmnt.com/did-you-know/brief-history-of-heavy-metals" rel="noopener noreferrer" target="_blank">A brief history of heavy metals in public health</a></li><li><a href="https://science.drinklmnt.com/did-you-know/toxins-vs-toxicology-why-dose-matters" rel="noopener noreferrer" target="_blank">Toxins vs. toxicology: Why dose matters</a></li><li><a href="https://science.drinklmnt.com/did-you-know/heavy-metal-regulations-proposition-65-explained" rel="noopener noreferrer" target="_blank">Understanding heavy metal regulations like Prop 65</a></li><li><a href="https://science.drinklmnt.com/did-you-know/does-body-absorb-heavy-metals-bioavailability-explained" rel="noopener noreferrer" target="_blank">Does your body absorb heavy metals? Bioavailability explained</a></li><li><a href="https://science.drinklmnt.com/did-you-know/detoxification-mechanisms-how-body-clears-heavy-metals" rel="noopener noreferrer" target="_blank">Mechanisms of detoxification: How the body clears heavy metals</a></li></ul> <h2>FAQs</h2>Q: What does 27 parts per billion mean? A: It means 27 micrograms of a substance in every kilogram (2.2 pounds) of food — roughly 27 grains of sand spread across a 10-mile beach. In a typical serving size, that translates to a fraction of a microgram, far less than what's naturally found in everyday foods like potatoes, lettuce, or carrots.Q: Should I worry about parts per billion in my food? A: Not usually. Parts per billion is an extremely small unit — one ppb is roughly a grain of sand on a 10-mile beach. Modern lab equipment can detect substances at this concentration, but detection isn't the same as danger. Most ppb measurements in food translate to a fraction of a microgram per serving, often lower than what's naturally present in vegetables, grains, and seafood. Run the math (ppb × serving size in grams ÷ 1,000) before reacting to a headline.Q: How do I calculate real serving amounts from lab report numbers? A: Multiply the ppb number by your serving size in grams, then divide by 1,000. That gives you micrograms per serving. For example, if a food contains 27 ppb of lead and the serving size is 3.5 grams: 27 × 3.5 ÷ 1,000 = 0.094 micrograms per serving. Lab reports list concentrations per kilogram for scientific accuracy, but a kilogram (2.2 pounds) is far more than a typical serving — which is why ppb numbers look bigger than what you'd consume.Q: Are heavy metals in food dangerous? A: Trace amounts of heavy metals occur naturally in nearly all food — including fruits, vegetables, and grains — because plants absorb minerals from soil and water. At these levels, your body's natural filtering systems process them without harm. What matters isn't whether a metal is detectable, but whether the dose is high enough to cause harm.